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Commit | Line | Data |
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ba9703b0 XL |
1 | //! Code for projecting associated types out of trait references. |
2 | ||
ba9703b0 XL |
3 | use super::specialization_graph; |
4 | use super::translate_substs; | |
5 | use super::util; | |
6 | use super::MismatchedProjectionTypes; | |
7 | use super::Obligation; | |
8 | use super::ObligationCause; | |
9 | use super::PredicateObligation; | |
10 | use super::Selection; | |
11 | use super::SelectionContext; | |
12 | use super::SelectionError; | |
f9f354fc | 13 | use super::{ |
f035d41b | 14 | ImplSourceClosureData, ImplSourceDiscriminantKindData, ImplSourceFnPointerData, |
6a06907d | 15 | ImplSourceGeneratorData, ImplSourcePointeeData, ImplSourceUserDefinedData, |
f9f354fc | 16 | }; |
f035d41b | 17 | use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey}; |
ba9703b0 XL |
18 | |
19 | use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; | |
20 | use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime}; | |
94222f64 | 21 | use crate::traits::error_reporting::InferCtxtExt as _; |
5099ac24 | 22 | use crate::traits::select::ProjectionMatchesProjection; |
3c0e092e | 23 | use rustc_data_structures::sso::SsoHashSet; |
f9f354fc | 24 | use rustc_data_structures::stack::ensure_sufficient_stack; |
ee023bcb | 25 | use rustc_errors::ErrorGuaranteed; |
5099ac24 | 26 | use rustc_hir::def::DefKind; |
ba9703b0 | 27 | use rustc_hir::def_id::DefId; |
3dfed10e | 28 | use rustc_hir::lang_items::LangItem; |
f035d41b | 29 | use rustc_infer::infer::resolve::OpportunisticRegionResolver; |
ee023bcb FG |
30 | use rustc_middle::traits::select::OverflowError; |
31 | use rustc_middle::ty::fold::{MaxUniverse, TypeFoldable, TypeFolder}; | |
f035d41b | 32 | use rustc_middle::ty::subst::Subst; |
5099ac24 | 33 | use rustc_middle::ty::{self, Term, ToPredicate, Ty, TyCtxt}; |
f035d41b | 34 | use rustc_span::symbol::sym; |
ba9703b0 | 35 | |
136023e0 XL |
36 | use std::collections::BTreeMap; |
37 | ||
ba9703b0 XL |
38 | pub use rustc_middle::traits::Reveal; |
39 | ||
40 | pub type PolyProjectionObligation<'tcx> = Obligation<'tcx, ty::PolyProjectionPredicate<'tcx>>; | |
41 | ||
42 | pub type ProjectionObligation<'tcx> = Obligation<'tcx, ty::ProjectionPredicate<'tcx>>; | |
43 | ||
44 | pub type ProjectionTyObligation<'tcx> = Obligation<'tcx, ty::ProjectionTy<'tcx>>; | |
45 | ||
f9652781 XL |
46 | pub(super) struct InProgress; |
47 | ||
ba9703b0 XL |
48 | /// When attempting to resolve `<T as TraitRef>::Name` ... |
49 | #[derive(Debug)] | |
5099ac24 | 50 | pub enum ProjectionError<'tcx> { |
ba9703b0 XL |
51 | /// ...we found multiple sources of information and couldn't resolve the ambiguity. |
52 | TooManyCandidates, | |
53 | ||
54 | /// ...an error occurred matching `T : TraitRef` | |
55 | TraitSelectionError(SelectionError<'tcx>), | |
56 | } | |
57 | ||
58 | #[derive(PartialEq, Eq, Debug)] | |
5099ac24 | 59 | enum ProjectionCandidate<'tcx> { |
29967ef6 | 60 | /// From a where-clause in the env or object type |
ba9703b0 XL |
61 | ParamEnv(ty::PolyProjectionPredicate<'tcx>), |
62 | ||
29967ef6 | 63 | /// From the definition of `Trait` when you have something like <<A as Trait>::B as Trait2>::C |
ba9703b0 XL |
64 | TraitDef(ty::PolyProjectionPredicate<'tcx>), |
65 | ||
29967ef6 XL |
66 | /// Bounds specified on an object type |
67 | Object(ty::PolyProjectionPredicate<'tcx>), | |
68 | ||
94222f64 | 69 | /// From an "impl" (or a "pseudo-impl" returned by select) |
ba9703b0 XL |
70 | Select(Selection<'tcx>), |
71 | } | |
72 | ||
5099ac24 | 73 | enum ProjectionCandidateSet<'tcx> { |
ba9703b0 | 74 | None, |
5099ac24 | 75 | Single(ProjectionCandidate<'tcx>), |
ba9703b0 XL |
76 | Ambiguous, |
77 | Error(SelectionError<'tcx>), | |
78 | } | |
79 | ||
5099ac24 | 80 | impl<'tcx> ProjectionCandidateSet<'tcx> { |
ba9703b0 | 81 | fn mark_ambiguous(&mut self) { |
5099ac24 | 82 | *self = ProjectionCandidateSet::Ambiguous; |
ba9703b0 XL |
83 | } |
84 | ||
85 | fn mark_error(&mut self, err: SelectionError<'tcx>) { | |
5099ac24 | 86 | *self = ProjectionCandidateSet::Error(err); |
ba9703b0 XL |
87 | } |
88 | ||
89 | // Returns true if the push was successful, or false if the candidate | |
90 | // was discarded -- this could be because of ambiguity, or because | |
91 | // a higher-priority candidate is already there. | |
5099ac24 FG |
92 | fn push_candidate(&mut self, candidate: ProjectionCandidate<'tcx>) -> bool { |
93 | use self::ProjectionCandidate::*; | |
94 | use self::ProjectionCandidateSet::*; | |
ba9703b0 XL |
95 | |
96 | // This wacky variable is just used to try and | |
97 | // make code readable and avoid confusing paths. | |
98 | // It is assigned a "value" of `()` only on those | |
99 | // paths in which we wish to convert `*self` to | |
100 | // ambiguous (and return false, because the candidate | |
101 | // was not used). On other paths, it is not assigned, | |
102 | // and hence if those paths *could* reach the code that | |
103 | // comes after the match, this fn would not compile. | |
104 | let convert_to_ambiguous; | |
105 | ||
106 | match self { | |
107 | None => { | |
108 | *self = Single(candidate); | |
109 | return true; | |
110 | } | |
111 | ||
112 | Single(current) => { | |
113 | // Duplicates can happen inside ParamEnv. In the case, we | |
114 | // perform a lazy deduplication. | |
115 | if current == &candidate { | |
116 | return false; | |
117 | } | |
118 | ||
119 | // Prefer where-clauses. As in select, if there are multiple | |
120 | // candidates, we prefer where-clause candidates over impls. This | |
121 | // may seem a bit surprising, since impls are the source of | |
122 | // "truth" in some sense, but in fact some of the impls that SEEM | |
123 | // applicable are not, because of nested obligations. Where | |
124 | // clauses are the safer choice. See the comment on | |
125 | // `select::SelectionCandidate` and #21974 for more details. | |
126 | match (current, candidate) { | |
127 | (ParamEnv(..), ParamEnv(..)) => convert_to_ambiguous = (), | |
128 | (ParamEnv(..), _) => return false, | |
129 | (_, ParamEnv(..)) => unreachable!(), | |
130 | (_, _) => convert_to_ambiguous = (), | |
131 | } | |
132 | } | |
133 | ||
134 | Ambiguous | Error(..) => { | |
135 | return false; | |
136 | } | |
137 | } | |
138 | ||
139 | // We only ever get here when we moved from a single candidate | |
140 | // to ambiguous. | |
141 | let () = convert_to_ambiguous; | |
142 | *self = Ambiguous; | |
143 | false | |
144 | } | |
145 | } | |
146 | ||
ee023bcb FG |
147 | /// Takes the place of a |
148 | /// Result< | |
149 | /// Result<Option<Vec<PredicateObligation<'tcx>>>, InProgress>, | |
150 | /// MismatchedProjectionTypes<'tcx>, | |
151 | /// > | |
152 | pub(super) enum ProjectAndUnifyResult<'tcx> { | |
153 | Holds(Vec<PredicateObligation<'tcx>>), | |
154 | FailedNormalization, | |
155 | Recursive, | |
156 | MismatchedProjectionTypes(MismatchedProjectionTypes<'tcx>), | |
157 | } | |
158 | ||
ba9703b0 XL |
159 | /// Evaluates constraints of the form: |
160 | /// | |
161 | /// for<...> <T as Trait>::U == V | |
162 | /// | |
163 | /// If successful, this may result in additional obligations. Also returns | |
164 | /// the projection cache key used to track these additional obligations. | |
f9652781 XL |
165 | /// |
166 | /// ## Returns | |
167 | /// | |
168 | /// - `Err(_)`: the projection can be normalized, but is not equal to the | |
169 | /// expected type. | |
170 | /// - `Ok(Err(InProgress))`: this is called recursively while normalizing | |
171 | /// the same projection. | |
172 | /// - `Ok(Ok(None))`: The projection cannot be normalized due to ambiguity | |
173 | /// (resolving some inference variables in the projection may fix this). | |
174 | /// - `Ok(Ok(Some(obligations)))`: The projection bound holds subject to | |
175 | /// the given obligations. If the projection cannot be normalized because | |
176 | /// the required trait bound doesn't hold this returned with `obligations` | |
177 | /// being a predicate that cannot be proven. | |
29967ef6 | 178 | #[instrument(level = "debug", skip(selcx))] |
f9652781 | 179 | pub(super) fn poly_project_and_unify_type<'cx, 'tcx>( |
ba9703b0 XL |
180 | selcx: &mut SelectionContext<'cx, 'tcx>, |
181 | obligation: &PolyProjectionObligation<'tcx>, | |
ee023bcb | 182 | ) -> ProjectAndUnifyResult<'tcx> { |
ba9703b0 | 183 | let infcx = selcx.infcx(); |
ee023bcb FG |
184 | let r = infcx.commit_if_ok(|_snapshot| { |
185 | let old_universe = infcx.universe(); | |
29967ef6 | 186 | let placeholder_predicate = |
fc512014 | 187 | infcx.replace_bound_vars_with_placeholders(obligation.predicate); |
ee023bcb | 188 | let new_universe = infcx.universe(); |
ba9703b0 XL |
189 | |
190 | let placeholder_obligation = obligation.with(placeholder_predicate); | |
ee023bcb FG |
191 | match project_and_unify_type(selcx, &placeholder_obligation) { |
192 | ProjectAndUnifyResult::MismatchedProjectionTypes(e) => Err(e), | |
193 | ProjectAndUnifyResult::Holds(obligations) | |
194 | if old_universe != new_universe | |
195 | && selcx.tcx().features().generic_associated_types_extended => | |
196 | { | |
197 | // If the `generic_associated_types_extended` feature is active, then we ignore any | |
198 | // obligations references lifetimes from any universe greater than or equal to the | |
199 | // universe just created. Otherwise, we can end up with something like `for<'a> I: 'a`, | |
200 | // which isn't quite what we want. Ideally, we want either an implied | |
201 | // `for<'a where I: 'a> I: 'a` or we want to "lazily" check these hold when we | |
202 | // substitute concrete regions. There is design work to be done here; until then, | |
203 | // however, this allows experimenting potential GAT features without running into | |
204 | // well-formedness issues. | |
205 | let new_obligations = obligations | |
206 | .into_iter() | |
207 | .filter(|obligation| { | |
208 | let mut visitor = MaxUniverse::new(); | |
209 | obligation.predicate.visit_with(&mut visitor); | |
210 | visitor.max_universe() < new_universe | |
211 | }) | |
212 | .collect(); | |
213 | Ok(ProjectAndUnifyResult::Holds(new_obligations)) | |
214 | } | |
215 | other => Ok(other), | |
216 | } | |
217 | }); | |
218 | ||
219 | match r { | |
220 | Ok(inner) => inner, | |
221 | Err(err) => ProjectAndUnifyResult::MismatchedProjectionTypes(err), | |
222 | } | |
ba9703b0 XL |
223 | } |
224 | ||
225 | /// Evaluates constraints of the form: | |
226 | /// | |
227 | /// <T as Trait>::U == V | |
228 | /// | |
229 | /// If successful, this may result in additional obligations. | |
f9652781 XL |
230 | /// |
231 | /// See [poly_project_and_unify_type] for an explanation of the return value. | |
ee023bcb | 232 | #[tracing::instrument(level = "debug", skip(selcx))] |
ba9703b0 XL |
233 | fn project_and_unify_type<'cx, 'tcx>( |
234 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
235 | obligation: &ProjectionObligation<'tcx>, | |
ee023bcb | 236 | ) -> ProjectAndUnifyResult<'tcx> { |
ba9703b0 | 237 | let mut obligations = vec![]; |
5099ac24 FG |
238 | |
239 | let infcx = selcx.infcx(); | |
240 | let normalized = match opt_normalize_projection_type( | |
ba9703b0 XL |
241 | selcx, |
242 | obligation.param_env, | |
243 | obligation.predicate.projection_ty, | |
244 | obligation.cause.clone(), | |
245 | obligation.recursion_depth, | |
246 | &mut obligations, | |
247 | ) { | |
f9652781 | 248 | Ok(Some(n)) => n, |
ee023bcb FG |
249 | Ok(None) => return ProjectAndUnifyResult::FailedNormalization, |
250 | Err(InProgress) => return ProjectAndUnifyResult::Recursive, | |
ba9703b0 | 251 | }; |
5099ac24 | 252 | debug!(?normalized, ?obligations, "project_and_unify_type result"); |
ee023bcb FG |
253 | let actual = obligation.predicate.term; |
254 | // HACK: lazy TAIT would regress src/test/ui/impl-trait/nested-return-type2.rs, so we add | |
255 | // a back-compat hack hat converts the RPITs into inference vars, just like they were before | |
256 | // lazy TAIT. | |
257 | // This does not affect TAITs in general, as tested in the nested-return-type-tait* tests. | |
258 | let InferOk { value: actual, obligations: new } = | |
259 | selcx.infcx().replace_opaque_types_with_inference_vars( | |
260 | actual, | |
261 | obligation.cause.body_id, | |
262 | obligation.cause.span, | |
263 | obligation.param_env, | |
264 | ); | |
265 | obligations.extend(new); | |
266 | ||
267 | match infcx.at(&obligation.cause, obligation.param_env).eq(normalized, actual) { | |
ba9703b0 XL |
268 | Ok(InferOk { obligations: inferred_obligations, value: () }) => { |
269 | obligations.extend(inferred_obligations); | |
ee023bcb | 270 | ProjectAndUnifyResult::Holds(obligations) |
ba9703b0 XL |
271 | } |
272 | Err(err) => { | |
ee023bcb FG |
273 | debug!("equating types encountered error {:?}", err); |
274 | ProjectAndUnifyResult::MismatchedProjectionTypes(MismatchedProjectionTypes { err }) | |
ba9703b0 XL |
275 | } |
276 | } | |
277 | } | |
278 | ||
279 | /// Normalizes any associated type projections in `value`, replacing | |
280 | /// them with a fully resolved type where possible. The return value | |
281 | /// combines the normalized result and any additional obligations that | |
282 | /// were incurred as result. | |
283 | pub fn normalize<'a, 'b, 'tcx, T>( | |
284 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
285 | param_env: ty::ParamEnv<'tcx>, | |
286 | cause: ObligationCause<'tcx>, | |
fc512014 | 287 | value: T, |
ba9703b0 XL |
288 | ) -> Normalized<'tcx, T> |
289 | where | |
290 | T: TypeFoldable<'tcx>, | |
291 | { | |
292 | let mut obligations = Vec::new(); | |
293 | let value = normalize_to(selcx, param_env, cause, value, &mut obligations); | |
294 | Normalized { value, obligations } | |
295 | } | |
296 | ||
297 | pub fn normalize_to<'a, 'b, 'tcx, T>( | |
298 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
299 | param_env: ty::ParamEnv<'tcx>, | |
300 | cause: ObligationCause<'tcx>, | |
fc512014 | 301 | value: T, |
ba9703b0 XL |
302 | obligations: &mut Vec<PredicateObligation<'tcx>>, |
303 | ) -> T | |
304 | where | |
305 | T: TypeFoldable<'tcx>, | |
306 | { | |
307 | normalize_with_depth_to(selcx, param_env, cause, 0, value, obligations) | |
308 | } | |
309 | ||
310 | /// As `normalize`, but with a custom depth. | |
311 | pub fn normalize_with_depth<'a, 'b, 'tcx, T>( | |
312 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
313 | param_env: ty::ParamEnv<'tcx>, | |
314 | cause: ObligationCause<'tcx>, | |
315 | depth: usize, | |
fc512014 | 316 | value: T, |
ba9703b0 XL |
317 | ) -> Normalized<'tcx, T> |
318 | where | |
319 | T: TypeFoldable<'tcx>, | |
320 | { | |
321 | let mut obligations = Vec::new(); | |
322 | let value = normalize_with_depth_to(selcx, param_env, cause, depth, value, &mut obligations); | |
323 | Normalized { value, obligations } | |
324 | } | |
325 | ||
136023e0 | 326 | #[instrument(level = "info", skip(selcx, param_env, cause, obligations))] |
ba9703b0 XL |
327 | pub fn normalize_with_depth_to<'a, 'b, 'tcx, T>( |
328 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
329 | param_env: ty::ParamEnv<'tcx>, | |
330 | cause: ObligationCause<'tcx>, | |
331 | depth: usize, | |
fc512014 | 332 | value: T, |
ba9703b0 XL |
333 | obligations: &mut Vec<PredicateObligation<'tcx>>, |
334 | ) -> T | |
335 | where | |
336 | T: TypeFoldable<'tcx>, | |
337 | { | |
136023e0 | 338 | debug!(obligations.len = obligations.len()); |
ba9703b0 | 339 | let mut normalizer = AssocTypeNormalizer::new(selcx, param_env, cause, depth, obligations); |
f9f354fc | 340 | let result = ensure_sufficient_stack(|| normalizer.fold(value)); |
29967ef6 XL |
341 | debug!(?result, obligations.len = normalizer.obligations.len()); |
342 | debug!(?normalizer.obligations,); | |
ba9703b0 XL |
343 | result |
344 | } | |
345 | ||
ee023bcb FG |
346 | #[instrument(level = "info", skip(selcx, param_env, cause, obligations))] |
347 | pub fn try_normalize_with_depth_to<'a, 'b, 'tcx, T>( | |
348 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
349 | param_env: ty::ParamEnv<'tcx>, | |
350 | cause: ObligationCause<'tcx>, | |
351 | depth: usize, | |
352 | value: T, | |
353 | obligations: &mut Vec<PredicateObligation<'tcx>>, | |
354 | ) -> T | |
355 | where | |
356 | T: TypeFoldable<'tcx>, | |
357 | { | |
358 | debug!(obligations.len = obligations.len()); | |
359 | let mut normalizer = AssocTypeNormalizer::new_without_eager_inference_replacement( | |
360 | selcx, | |
361 | param_env, | |
362 | cause, | |
363 | depth, | |
364 | obligations, | |
365 | ); | |
366 | let result = ensure_sufficient_stack(|| normalizer.fold(value)); | |
367 | debug!(?result, obligations.len = normalizer.obligations.len()); | |
368 | debug!(?normalizer.obligations,); | |
369 | result | |
370 | } | |
371 | ||
136023e0 XL |
372 | pub(crate) fn needs_normalization<'tcx, T: TypeFoldable<'tcx>>(value: &T, reveal: Reveal) -> bool { |
373 | match reveal { | |
374 | Reveal::UserFacing => value | |
375 | .has_type_flags(ty::TypeFlags::HAS_TY_PROJECTION | ty::TypeFlags::HAS_CT_PROJECTION), | |
376 | Reveal::All => value.has_type_flags( | |
377 | ty::TypeFlags::HAS_TY_PROJECTION | |
378 | | ty::TypeFlags::HAS_TY_OPAQUE | |
379 | | ty::TypeFlags::HAS_CT_PROJECTION, | |
380 | ), | |
381 | } | |
382 | } | |
383 | ||
ba9703b0 XL |
384 | struct AssocTypeNormalizer<'a, 'b, 'tcx> { |
385 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
386 | param_env: ty::ParamEnv<'tcx>, | |
387 | cause: ObligationCause<'tcx>, | |
388 | obligations: &'a mut Vec<PredicateObligation<'tcx>>, | |
389 | depth: usize, | |
136023e0 | 390 | universes: Vec<Option<ty::UniverseIndex>>, |
ee023bcb FG |
391 | /// If true, when a projection is unable to be completed, an inference |
392 | /// variable will be created and an obligation registered to project to that | |
393 | /// inference variable. Also, constants will be eagerly evaluated. | |
394 | eager_inference_replacement: bool, | |
ba9703b0 XL |
395 | } |
396 | ||
397 | impl<'a, 'b, 'tcx> AssocTypeNormalizer<'a, 'b, 'tcx> { | |
398 | fn new( | |
399 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
400 | param_env: ty::ParamEnv<'tcx>, | |
401 | cause: ObligationCause<'tcx>, | |
402 | depth: usize, | |
403 | obligations: &'a mut Vec<PredicateObligation<'tcx>>, | |
404 | ) -> AssocTypeNormalizer<'a, 'b, 'tcx> { | |
ee023bcb FG |
405 | AssocTypeNormalizer { |
406 | selcx, | |
407 | param_env, | |
408 | cause, | |
409 | obligations, | |
410 | depth, | |
411 | universes: vec![], | |
412 | eager_inference_replacement: true, | |
413 | } | |
414 | } | |
415 | ||
416 | fn new_without_eager_inference_replacement( | |
417 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
418 | param_env: ty::ParamEnv<'tcx>, | |
419 | cause: ObligationCause<'tcx>, | |
420 | depth: usize, | |
421 | obligations: &'a mut Vec<PredicateObligation<'tcx>>, | |
422 | ) -> AssocTypeNormalizer<'a, 'b, 'tcx> { | |
423 | AssocTypeNormalizer { | |
424 | selcx, | |
425 | param_env, | |
426 | cause, | |
427 | obligations, | |
428 | depth, | |
429 | universes: vec![], | |
430 | eager_inference_replacement: false, | |
431 | } | |
ba9703b0 XL |
432 | } |
433 | ||
fc512014 | 434 | fn fold<T: TypeFoldable<'tcx>>(&mut self, value: T) -> T { |
ba9703b0 | 435 | let value = self.selcx.infcx().resolve_vars_if_possible(value); |
136023e0 XL |
436 | debug!(?value); |
437 | ||
438 | assert!( | |
439 | !value.has_escaping_bound_vars(), | |
440 | "Normalizing {:?} without wrapping in a `Binder`", | |
441 | value | |
442 | ); | |
ba9703b0 | 443 | |
136023e0 XL |
444 | if !needs_normalization(&value, self.param_env.reveal()) { |
445 | value | |
446 | } else { | |
447 | value.fold_with(self) | |
448 | } | |
ba9703b0 XL |
449 | } |
450 | } | |
451 | ||
452 | impl<'a, 'b, 'tcx> TypeFolder<'tcx> for AssocTypeNormalizer<'a, 'b, 'tcx> { | |
453 | fn tcx<'c>(&'c self) -> TyCtxt<'tcx> { | |
454 | self.selcx.tcx() | |
455 | } | |
456 | ||
136023e0 XL |
457 | fn fold_binder<T: TypeFoldable<'tcx>>( |
458 | &mut self, | |
459 | t: ty::Binder<'tcx, T>, | |
460 | ) -> ty::Binder<'tcx, T> { | |
461 | self.universes.push(None); | |
462 | let t = t.super_fold_with(self); | |
463 | self.universes.pop(); | |
464 | t | |
465 | } | |
466 | ||
ba9703b0 | 467 | fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
136023e0 | 468 | if !needs_normalization(&ty, self.param_env.reveal()) { |
ba9703b0 XL |
469 | return ty; |
470 | } | |
94222f64 XL |
471 | |
472 | // We try to be a little clever here as a performance optimization in | |
473 | // cases where there are nested projections under binders. | |
474 | // For example: | |
475 | // ``` | |
476 | // for<'a> fn(<T as Foo>::One<'a, Box<dyn Bar<'a, Item=<T as Foo>::Two<'a>>>>) | |
477 | // ``` | |
478 | // We normalize the substs on the projection before the projecting, but | |
479 | // if we're naive, we'll | |
480 | // replace bound vars on inner, project inner, replace placeholders on inner, | |
481 | // replace bound vars on outer, project outer, replace placeholders on outer | |
ba9703b0 | 482 | // |
94222f64 XL |
483 | // However, if we're a bit more clever, we can replace the bound vars |
484 | // on the entire type before normalizing nested projections, meaning we | |
485 | // replace bound vars on outer, project inner, | |
486 | // project outer, replace placeholders on outer | |
ba9703b0 | 487 | // |
94222f64 XL |
488 | // This is possible because the inner `'a` will already be a placeholder |
489 | // when we need to normalize the inner projection | |
ba9703b0 | 490 | // |
94222f64 XL |
491 | // On the other hand, this does add a bit of complexity, since we only |
492 | // replace bound vars if the current type is a `Projection` and we need | |
493 | // to make sure we don't forget to fold the substs regardless. | |
ba9703b0 | 494 | |
1b1a35ee | 495 | match *ty.kind() { |
94222f64 XL |
496 | // This is really important. While we *can* handle this, this has |
497 | // severe performance implications for large opaque types with | |
498 | // late-bound regions. See `issue-88862` benchmark. | |
1b1a35ee | 499 | ty::Opaque(def_id, substs) if !substs.has_escaping_bound_vars() => { |
5099ac24 | 500 | // Only normalize `impl Trait` outside of type inference, usually in codegen. |
f035d41b | 501 | match self.param_env.reveal() { |
94222f64 | 502 | Reveal::UserFacing => ty.super_fold_with(self), |
ba9703b0 XL |
503 | |
504 | Reveal::All => { | |
136023e0 | 505 | let recursion_limit = self.tcx().recursion_limit(); |
f9f354fc | 506 | if !recursion_limit.value_within_limit(self.depth) { |
ba9703b0 XL |
507 | let obligation = Obligation::with_depth( |
508 | self.cause.clone(), | |
f9f354fc | 509 | recursion_limit.0, |
ba9703b0 XL |
510 | self.param_env, |
511 | ty, | |
512 | ); | |
513 | self.selcx.infcx().report_overflow_error(&obligation, true); | |
514 | } | |
515 | ||
94222f64 | 516 | let substs = substs.super_fold_with(self); |
ba9703b0 XL |
517 | let generic_ty = self.tcx().type_of(def_id); |
518 | let concrete_ty = generic_ty.subst(self.tcx(), substs); | |
519 | self.depth += 1; | |
520 | let folded_ty = self.fold_ty(concrete_ty); | |
521 | self.depth -= 1; | |
522 | folded_ty | |
523 | } | |
524 | } | |
525 | } | |
526 | ||
fc512014 | 527 | ty::Projection(data) if !data.has_escaping_bound_vars() => { |
94222f64 XL |
528 | // This branch is *mostly* just an optimization: when we don't |
529 | // have escaping bound vars, we don't need to replace them with | |
530 | // placeholders (see branch below). *Also*, we know that we can | |
531 | // register an obligation to *later* project, since we know | |
532 | // there won't be bound vars there. | |
ba9703b0 | 533 | |
94222f64 | 534 | let data = data.super_fold_with(self); |
ee023bcb FG |
535 | let normalized_ty = if self.eager_inference_replacement { |
536 | normalize_projection_type( | |
537 | self.selcx, | |
538 | self.param_env, | |
539 | data, | |
540 | self.cause.clone(), | |
541 | self.depth, | |
542 | &mut self.obligations, | |
543 | ) | |
544 | } else { | |
545 | opt_normalize_projection_type( | |
546 | self.selcx, | |
547 | self.param_env, | |
548 | data, | |
549 | self.cause.clone(), | |
550 | self.depth, | |
551 | &mut self.obligations, | |
552 | ) | |
553 | .ok() | |
554 | .flatten() | |
555 | .unwrap_or_else(|| ty::Term::Ty(ty.super_fold_with(self))) | |
556 | }; | |
ba9703b0 | 557 | debug!( |
29967ef6 XL |
558 | ?self.depth, |
559 | ?ty, | |
560 | ?normalized_ty, | |
561 | obligations.len = ?self.obligations.len(), | |
562 | "AssocTypeNormalizer: normalized type" | |
ba9703b0 | 563 | ); |
5099ac24 | 564 | normalized_ty.ty().unwrap() |
ba9703b0 XL |
565 | } |
566 | ||
94222f64 XL |
567 | ty::Projection(data) => { |
568 | // If there are escaping bound vars, we temporarily replace the | |
569 | // bound vars with placeholders. Note though, that in the case | |
570 | // that we still can't project for whatever reason (e.g. self | |
571 | // type isn't known enough), we *can't* register an obligation | |
572 | // and return an inference variable (since then that obligation | |
573 | // would have bound vars and that's a can of worms). Instead, | |
574 | // we just give up and fall back to pretending like we never tried! | |
575 | // | |
576 | // Note: this isn't necessarily the final approach here; we may | |
577 | // want to figure out how to register obligations with escaping vars | |
578 | // or handle this some other way. | |
136023e0 XL |
579 | |
580 | let infcx = self.selcx.infcx(); | |
581 | let (data, mapped_regions, mapped_types, mapped_consts) = | |
582 | BoundVarReplacer::replace_bound_vars(infcx, &mut self.universes, data); | |
94222f64 | 583 | let data = data.super_fold_with(self); |
136023e0 XL |
584 | let normalized_ty = opt_normalize_projection_type( |
585 | self.selcx, | |
586 | self.param_env, | |
587 | data, | |
588 | self.cause.clone(), | |
589 | self.depth, | |
590 | &mut self.obligations, | |
591 | ) | |
592 | .ok() | |
593 | .flatten() | |
5099ac24 | 594 | .map(|term| term.ty().unwrap()) |
94222f64 XL |
595 | .map(|normalized_ty| { |
596 | PlaceholderReplacer::replace_placeholders( | |
597 | infcx, | |
598 | mapped_regions, | |
599 | mapped_types, | |
600 | mapped_consts, | |
601 | &self.universes, | |
602 | normalized_ty, | |
603 | ) | |
604 | }) | |
605 | .unwrap_or_else(|| ty.super_fold_with(self)); | |
606 | ||
136023e0 XL |
607 | debug!( |
608 | ?self.depth, | |
609 | ?ty, | |
610 | ?normalized_ty, | |
611 | obligations.len = ?self.obligations.len(), | |
612 | "AssocTypeNormalizer: normalized type" | |
613 | ); | |
614 | normalized_ty | |
615 | } | |
616 | ||
94222f64 | 617 | _ => ty.super_fold_with(self), |
ba9703b0 XL |
618 | } |
619 | } | |
620 | ||
5099ac24 | 621 | fn fold_const(&mut self, constant: ty::Const<'tcx>) -> ty::Const<'tcx> { |
ee023bcb | 622 | if self.selcx.tcx().lazy_normalization() || !self.eager_inference_replacement { |
f9f354fc XL |
623 | constant |
624 | } else { | |
625 | let constant = constant.super_fold_with(self); | |
626 | constant.eval(self.selcx.tcx(), self.param_env) | |
627 | } | |
ba9703b0 XL |
628 | } |
629 | } | |
630 | ||
136023e0 XL |
631 | pub struct BoundVarReplacer<'me, 'tcx> { |
632 | infcx: &'me InferCtxt<'me, 'tcx>, | |
633 | // These three maps track the bound variable that were replaced by placeholders. It might be | |
634 | // nice to remove these since we already have the `kind` in the placeholder; we really just need | |
635 | // the `var` (but we *could* bring that into scope if we were to track them as we pass them). | |
636 | mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>, | |
637 | mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy>, | |
638 | mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>, | |
639 | // The current depth relative to *this* folding, *not* the entire normalization. In other words, | |
640 | // the depth of binders we've passed here. | |
641 | current_index: ty::DebruijnIndex, | |
642 | // The `UniverseIndex` of the binding levels above us. These are optional, since we are lazy: | |
643 | // we don't actually create a universe until we see a bound var we have to replace. | |
644 | universe_indices: &'me mut Vec<Option<ty::UniverseIndex>>, | |
645 | } | |
646 | ||
647 | impl<'me, 'tcx> BoundVarReplacer<'me, 'tcx> { | |
648 | /// Returns `Some` if we *were* able to replace bound vars. If there are any bound vars that | |
649 | /// use a binding level above `universe_indices.len()`, we fail. | |
650 | pub fn replace_bound_vars<T: TypeFoldable<'tcx>>( | |
651 | infcx: &'me InferCtxt<'me, 'tcx>, | |
652 | universe_indices: &'me mut Vec<Option<ty::UniverseIndex>>, | |
653 | value: T, | |
654 | ) -> ( | |
655 | T, | |
656 | BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>, | |
657 | BTreeMap<ty::PlaceholderType, ty::BoundTy>, | |
658 | BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>, | |
659 | ) { | |
660 | let mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion> = BTreeMap::new(); | |
661 | let mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy> = BTreeMap::new(); | |
662 | let mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar> = BTreeMap::new(); | |
663 | ||
664 | let mut replacer = BoundVarReplacer { | |
665 | infcx, | |
666 | mapped_regions, | |
667 | mapped_types, | |
668 | mapped_consts, | |
669 | current_index: ty::INNERMOST, | |
670 | universe_indices, | |
671 | }; | |
672 | ||
673 | let value = value.super_fold_with(&mut replacer); | |
674 | ||
675 | (value, replacer.mapped_regions, replacer.mapped_types, replacer.mapped_consts) | |
676 | } | |
677 | ||
678 | fn universe_for(&mut self, debruijn: ty::DebruijnIndex) -> ty::UniverseIndex { | |
679 | let infcx = self.infcx; | |
680 | let index = | |
c295e0f8 | 681 | self.universe_indices.len() + self.current_index.as_usize() - debruijn.as_usize() - 1; |
136023e0 XL |
682 | let universe = self.universe_indices[index].unwrap_or_else(|| { |
683 | for i in self.universe_indices.iter_mut().take(index + 1) { | |
684 | *i = i.or_else(|| Some(infcx.create_next_universe())) | |
685 | } | |
686 | self.universe_indices[index].unwrap() | |
687 | }); | |
688 | universe | |
689 | } | |
690 | } | |
691 | ||
a2a8927a | 692 | impl<'tcx> TypeFolder<'tcx> for BoundVarReplacer<'_, 'tcx> { |
136023e0 XL |
693 | fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
694 | self.infcx.tcx | |
695 | } | |
696 | ||
697 | fn fold_binder<T: TypeFoldable<'tcx>>( | |
698 | &mut self, | |
699 | t: ty::Binder<'tcx, T>, | |
700 | ) -> ty::Binder<'tcx, T> { | |
701 | self.current_index.shift_in(1); | |
702 | let t = t.super_fold_with(self); | |
703 | self.current_index.shift_out(1); | |
704 | t | |
705 | } | |
706 | ||
707 | fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
708 | match *r { | |
709 | ty::ReLateBound(debruijn, _) | |
710 | if debruijn.as_usize() + 1 | |
711 | > self.current_index.as_usize() + self.universe_indices.len() => | |
712 | { | |
713 | bug!("Bound vars outside of `self.universe_indices`"); | |
714 | } | |
715 | ty::ReLateBound(debruijn, br) if debruijn >= self.current_index => { | |
716 | let universe = self.universe_for(debruijn); | |
717 | let p = ty::PlaceholderRegion { universe, name: br.kind }; | |
c295e0f8 | 718 | self.mapped_regions.insert(p, br); |
136023e0 XL |
719 | self.infcx.tcx.mk_region(ty::RePlaceholder(p)) |
720 | } | |
721 | _ => r, | |
722 | } | |
723 | } | |
724 | ||
725 | fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { | |
726 | match *t.kind() { | |
727 | ty::Bound(debruijn, _) | |
728 | if debruijn.as_usize() + 1 | |
729 | > self.current_index.as_usize() + self.universe_indices.len() => | |
730 | { | |
731 | bug!("Bound vars outside of `self.universe_indices`"); | |
732 | } | |
733 | ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => { | |
734 | let universe = self.universe_for(debruijn); | |
735 | let p = ty::PlaceholderType { universe, name: bound_ty.var }; | |
c295e0f8 | 736 | self.mapped_types.insert(p, bound_ty); |
136023e0 XL |
737 | self.infcx.tcx.mk_ty(ty::Placeholder(p)) |
738 | } | |
739 | _ if t.has_vars_bound_at_or_above(self.current_index) => t.super_fold_with(self), | |
740 | _ => t, | |
741 | } | |
742 | } | |
743 | ||
5099ac24 FG |
744 | fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { |
745 | match ct.val() { | |
746 | ty::ConstKind::Bound(debruijn, _) | |
136023e0 XL |
747 | if debruijn.as_usize() + 1 |
748 | > self.current_index.as_usize() + self.universe_indices.len() => | |
749 | { | |
750 | bug!("Bound vars outside of `self.universe_indices`"); | |
751 | } | |
5099ac24 | 752 | ty::ConstKind::Bound(debruijn, bound_const) if debruijn >= self.current_index => { |
136023e0 XL |
753 | let universe = self.universe_for(debruijn); |
754 | let p = ty::PlaceholderConst { | |
755 | universe, | |
5099ac24 | 756 | name: ty::BoundConst { var: bound_const, ty: ct.ty() }, |
136023e0 | 757 | }; |
c295e0f8 | 758 | self.mapped_consts.insert(p, bound_const); |
5099ac24 FG |
759 | self.infcx |
760 | .tcx | |
761 | .mk_const(ty::ConstS { val: ty::ConstKind::Placeholder(p), ty: ct.ty() }) | |
136023e0 XL |
762 | } |
763 | _ if ct.has_vars_bound_at_or_above(self.current_index) => ct.super_fold_with(self), | |
764 | _ => ct, | |
765 | } | |
766 | } | |
767 | } | |
768 | ||
769 | // The inverse of `BoundVarReplacer`: replaces placeholders with the bound vars from which they came. | |
770 | pub struct PlaceholderReplacer<'me, 'tcx> { | |
771 | infcx: &'me InferCtxt<'me, 'tcx>, | |
772 | mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>, | |
773 | mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy>, | |
774 | mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>, | |
775 | universe_indices: &'me Vec<Option<ty::UniverseIndex>>, | |
776 | current_index: ty::DebruijnIndex, | |
777 | } | |
778 | ||
779 | impl<'me, 'tcx> PlaceholderReplacer<'me, 'tcx> { | |
780 | pub fn replace_placeholders<T: TypeFoldable<'tcx>>( | |
781 | infcx: &'me InferCtxt<'me, 'tcx>, | |
782 | mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>, | |
783 | mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy>, | |
784 | mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>, | |
785 | universe_indices: &'me Vec<Option<ty::UniverseIndex>>, | |
786 | value: T, | |
787 | ) -> T { | |
788 | let mut replacer = PlaceholderReplacer { | |
789 | infcx, | |
790 | mapped_regions, | |
791 | mapped_types, | |
792 | mapped_consts, | |
793 | universe_indices, | |
794 | current_index: ty::INNERMOST, | |
795 | }; | |
796 | value.super_fold_with(&mut replacer) | |
797 | } | |
798 | } | |
799 | ||
a2a8927a | 800 | impl<'tcx> TypeFolder<'tcx> for PlaceholderReplacer<'_, 'tcx> { |
136023e0 XL |
801 | fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
802 | self.infcx.tcx | |
803 | } | |
804 | ||
805 | fn fold_binder<T: TypeFoldable<'tcx>>( | |
806 | &mut self, | |
807 | t: ty::Binder<'tcx, T>, | |
808 | ) -> ty::Binder<'tcx, T> { | |
809 | if !t.has_placeholders() && !t.has_infer_regions() { | |
810 | return t; | |
811 | } | |
812 | self.current_index.shift_in(1); | |
813 | let t = t.super_fold_with(self); | |
814 | self.current_index.shift_out(1); | |
815 | t | |
816 | } | |
817 | ||
818 | fn fold_region(&mut self, r0: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
5099ac24 | 819 | let r1 = match *r0 { |
136023e0 XL |
820 | ty::ReVar(_) => self |
821 | .infcx | |
822 | .inner | |
823 | .borrow_mut() | |
824 | .unwrap_region_constraints() | |
825 | .opportunistic_resolve_region(self.infcx.tcx, r0), | |
826 | _ => r0, | |
827 | }; | |
828 | ||
829 | let r2 = match *r1 { | |
830 | ty::RePlaceholder(p) => { | |
831 | let replace_var = self.mapped_regions.get(&p); | |
832 | match replace_var { | |
833 | Some(replace_var) => { | |
834 | let index = self | |
835 | .universe_indices | |
836 | .iter() | |
837 | .position(|u| matches!(u, Some(pu) if *pu == p.universe)) | |
838 | .unwrap_or_else(|| bug!("Unexpected placeholder universe.")); | |
839 | let db = ty::DebruijnIndex::from_usize( | |
840 | self.universe_indices.len() - index + self.current_index.as_usize() - 1, | |
841 | ); | |
842 | self.tcx().mk_region(ty::ReLateBound(db, *replace_var)) | |
843 | } | |
844 | None => r1, | |
845 | } | |
846 | } | |
847 | _ => r1, | |
848 | }; | |
849 | ||
850 | debug!(?r0, ?r1, ?r2, "fold_region"); | |
851 | ||
852 | r2 | |
853 | } | |
854 | ||
855 | fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { | |
856 | match *ty.kind() { | |
857 | ty::Placeholder(p) => { | |
858 | let replace_var = self.mapped_types.get(&p); | |
859 | match replace_var { | |
860 | Some(replace_var) => { | |
861 | let index = self | |
862 | .universe_indices | |
863 | .iter() | |
864 | .position(|u| matches!(u, Some(pu) if *pu == p.universe)) | |
865 | .unwrap_or_else(|| bug!("Unexpected placeholder universe.")); | |
866 | let db = ty::DebruijnIndex::from_usize( | |
867 | self.universe_indices.len() - index + self.current_index.as_usize() - 1, | |
868 | ); | |
869 | self.tcx().mk_ty(ty::Bound(db, *replace_var)) | |
870 | } | |
871 | None => ty, | |
872 | } | |
873 | } | |
874 | ||
875 | _ if ty.has_placeholders() || ty.has_infer_regions() => ty.super_fold_with(self), | |
876 | _ => ty, | |
877 | } | |
878 | } | |
879 | ||
5099ac24 FG |
880 | fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { |
881 | if let ty::ConstKind::Placeholder(p) = ct.val() { | |
136023e0 XL |
882 | let replace_var = self.mapped_consts.get(&p); |
883 | match replace_var { | |
884 | Some(replace_var) => { | |
885 | let index = self | |
886 | .universe_indices | |
887 | .iter() | |
888 | .position(|u| matches!(u, Some(pu) if *pu == p.universe)) | |
889 | .unwrap_or_else(|| bug!("Unexpected placeholder universe.")); | |
890 | let db = ty::DebruijnIndex::from_usize( | |
891 | self.universe_indices.len() - index + self.current_index.as_usize() - 1, | |
892 | ); | |
5099ac24 FG |
893 | self.tcx().mk_const(ty::ConstS { |
894 | val: ty::ConstKind::Bound(db, *replace_var), | |
895 | ty: ct.ty(), | |
896 | }) | |
136023e0 XL |
897 | } |
898 | None => ct, | |
899 | } | |
900 | } else { | |
901 | ct.super_fold_with(self) | |
902 | } | |
903 | } | |
904 | } | |
905 | ||
ba9703b0 XL |
906 | /// The guts of `normalize`: normalize a specific projection like `<T |
907 | /// as Trait>::Item`. The result is always a type (and possibly | |
908 | /// additional obligations). If ambiguity arises, which implies that | |
909 | /// there are unresolved type variables in the projection, we will | |
910 | /// substitute a fresh type variable `$X` and generate a new | |
911 | /// obligation `<T as Trait>::Item == $X` for later. | |
912 | pub fn normalize_projection_type<'a, 'b, 'tcx>( | |
913 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
914 | param_env: ty::ParamEnv<'tcx>, | |
915 | projection_ty: ty::ProjectionTy<'tcx>, | |
916 | cause: ObligationCause<'tcx>, | |
917 | depth: usize, | |
918 | obligations: &mut Vec<PredicateObligation<'tcx>>, | |
5099ac24 | 919 | ) -> Term<'tcx> { |
ba9703b0 XL |
920 | opt_normalize_projection_type( |
921 | selcx, | |
922 | param_env, | |
923 | projection_ty, | |
924 | cause.clone(), | |
925 | depth, | |
926 | obligations, | |
927 | ) | |
f9652781 XL |
928 | .ok() |
929 | .flatten() | |
ba9703b0 XL |
930 | .unwrap_or_else(move || { |
931 | // if we bottom out in ambiguity, create a type variable | |
932 | // and a deferred predicate to resolve this when more type | |
933 | // information is available. | |
934 | ||
5099ac24 FG |
935 | selcx |
936 | .infcx() | |
937 | .infer_projection(param_env, projection_ty, cause, depth + 1, obligations) | |
938 | .into() | |
ba9703b0 XL |
939 | }) |
940 | } | |
941 | ||
942 | /// The guts of `normalize`: normalize a specific projection like `<T | |
943 | /// as Trait>::Item`. The result is always a type (and possibly | |
944 | /// additional obligations). Returns `None` in the case of ambiguity, | |
945 | /// which indicates that there are unbound type variables. | |
946 | /// | |
947 | /// This function used to return `Option<NormalizedTy<'tcx>>`, which contains a | |
948 | /// `Ty<'tcx>` and an obligations vector. But that obligation vector was very | |
949 | /// often immediately appended to another obligations vector. So now this | |
950 | /// function takes an obligations vector and appends to it directly, which is | |
951 | /// slightly uglier but avoids the need for an extra short-lived allocation. | |
29967ef6 | 952 | #[instrument(level = "debug", skip(selcx, param_env, cause, obligations))] |
ba9703b0 XL |
953 | fn opt_normalize_projection_type<'a, 'b, 'tcx>( |
954 | selcx: &'a mut SelectionContext<'b, 'tcx>, | |
955 | param_env: ty::ParamEnv<'tcx>, | |
956 | projection_ty: ty::ProjectionTy<'tcx>, | |
957 | cause: ObligationCause<'tcx>, | |
958 | depth: usize, | |
959 | obligations: &mut Vec<PredicateObligation<'tcx>>, | |
5099ac24 | 960 | ) -> Result<Option<Term<'tcx>>, InProgress> { |
ba9703b0 | 961 | let infcx = selcx.infcx(); |
94222f64 XL |
962 | // Don't use the projection cache in intercrate mode - |
963 | // the `infcx` may be re-used between intercrate in non-intercrate | |
964 | // mode, which could lead to using incorrect cache results. | |
965 | let use_cache = !selcx.is_intercrate(); | |
ba9703b0 | 966 | |
fc512014 | 967 | let projection_ty = infcx.resolve_vars_if_possible(projection_ty); |
ba9703b0 XL |
968 | let cache_key = ProjectionCacheKey::new(projection_ty); |
969 | ||
ba9703b0 XL |
970 | // FIXME(#20304) For now, I am caching here, which is good, but it |
971 | // means we don't capture the type variables that are created in | |
972 | // the case of ambiguity. Which means we may create a large stream | |
973 | // of such variables. OTOH, if we move the caching up a level, we | |
974 | // would not benefit from caching when proving `T: Trait<U=Foo>` | |
975 | // bounds. It might be the case that we want two distinct caches, | |
976 | // or else another kind of cache entry. | |
977 | ||
94222f64 XL |
978 | let cache_result = if use_cache { |
979 | infcx.inner.borrow_mut().projection_cache().try_start(cache_key) | |
980 | } else { | |
981 | Ok(()) | |
982 | }; | |
ba9703b0 | 983 | match cache_result { |
136023e0 | 984 | Ok(()) => debug!("no cache"), |
ba9703b0 XL |
985 | Err(ProjectionCacheEntry::Ambiguous) => { |
986 | // If we found ambiguity the last time, that means we will continue | |
987 | // to do so until some type in the key changes (and we know it | |
988 | // hasn't, because we just fully resolved it). | |
29967ef6 | 989 | debug!("found cache entry: ambiguous"); |
f9652781 | 990 | return Ok(None); |
ba9703b0 XL |
991 | } |
992 | Err(ProjectionCacheEntry::InProgress) => { | |
ba9703b0 XL |
993 | // Under lazy normalization, this can arise when |
994 | // bootstrapping. That is, imagine an environment with a | |
995 | // where-clause like `A::B == u32`. Now, if we are asked | |
996 | // to normalize `A::B`, we will want to check the | |
997 | // where-clauses in scope. So we will try to unify `A::B` | |
998 | // with `A::B`, which can trigger a recursive | |
f9652781 | 999 | // normalization. |
ba9703b0 | 1000 | |
29967ef6 | 1001 | debug!("found cache entry: in-progress"); |
ba9703b0 | 1002 | |
b9856134 XL |
1003 | // Cache that normalizing this projection resulted in a cycle. This |
1004 | // should ensure that, unless this happens within a snapshot that's | |
1005 | // rolled back, fulfillment or evaluation will notice the cycle. | |
1006 | ||
94222f64 XL |
1007 | if use_cache { |
1008 | infcx.inner.borrow_mut().projection_cache().recur(cache_key); | |
1009 | } | |
b9856134 XL |
1010 | return Err(InProgress); |
1011 | } | |
1012 | Err(ProjectionCacheEntry::Recur) => { | |
136023e0 | 1013 | debug!("recur cache"); |
f9652781 | 1014 | return Err(InProgress); |
ba9703b0 | 1015 | } |
a2a8927a | 1016 | Err(ProjectionCacheEntry::NormalizedTy { ty, complete: _ }) => { |
ba9703b0 XL |
1017 | // This is the hottest path in this function. |
1018 | // | |
1019 | // If we find the value in the cache, then return it along | |
1020 | // with the obligations that went along with it. Note | |
1021 | // that, when using a fulfillment context, these | |
1022 | // obligations could in principle be ignored: they have | |
1023 | // already been registered when the cache entry was | |
1024 | // created (and hence the new ones will quickly be | |
1025 | // discarded as duplicated). But when doing trait | |
1026 | // evaluation this is not the case, and dropping the trait | |
1027 | // evaluations can causes ICEs (e.g., #43132). | |
29967ef6 | 1028 | debug!(?ty, "found normalized ty"); |
17df50a5 | 1029 | obligations.extend(ty.obligations); |
f9652781 | 1030 | return Ok(Some(ty.value)); |
ba9703b0 XL |
1031 | } |
1032 | Err(ProjectionCacheEntry::Error) => { | |
29967ef6 | 1033 | debug!("opt_normalize_projection_type: found error"); |
ba9703b0 XL |
1034 | let result = normalize_to_error(selcx, param_env, projection_ty, cause, depth); |
1035 | obligations.extend(result.obligations); | |
5099ac24 | 1036 | return Ok(Some(result.value.into())); |
ba9703b0 XL |
1037 | } |
1038 | } | |
1039 | ||
1040 | let obligation = Obligation::with_depth(cause.clone(), depth, param_env, projection_ty); | |
94222f64 | 1041 | |
5099ac24 FG |
1042 | match project(selcx, &obligation) { |
1043 | Ok(Projected::Progress(Progress { | |
1044 | term: projected_term, | |
ba9703b0 XL |
1045 | obligations: mut projected_obligations, |
1046 | })) => { | |
1047 | // if projection succeeded, then what we get out of this | |
1048 | // is also non-normalized (consider: it was derived from | |
1049 | // an impl, where-clause etc) and hence we must | |
1050 | // re-normalize it | |
1051 | ||
5099ac24 | 1052 | let projected_term = selcx.infcx().resolve_vars_if_possible(projected_term); |
ba9703b0 | 1053 | |
5099ac24 | 1054 | let mut result = if projected_term.has_projections() { |
ba9703b0 XL |
1055 | let mut normalizer = AssocTypeNormalizer::new( |
1056 | selcx, | |
1057 | param_env, | |
1058 | cause, | |
1059 | depth + 1, | |
1060 | &mut projected_obligations, | |
1061 | ); | |
5099ac24 | 1062 | let normalized_ty = normalizer.fold(projected_term); |
ba9703b0 XL |
1063 | |
1064 | Normalized { value: normalized_ty, obligations: projected_obligations } | |
1065 | } else { | |
5099ac24 | 1066 | Normalized { value: projected_term, obligations: projected_obligations } |
ba9703b0 XL |
1067 | }; |
1068 | ||
3c0e092e | 1069 | let mut deduped: SsoHashSet<_> = Default::default(); |
94222f64 | 1070 | result.obligations.drain_filter(|projected_obligation| { |
3c0e092e XL |
1071 | if !deduped.insert(projected_obligation.clone()) { |
1072 | return true; | |
1073 | } | |
a2a8927a | 1074 | false |
94222f64 XL |
1075 | }); |
1076 | ||
1077 | if use_cache { | |
5099ac24 | 1078 | infcx.inner.borrow_mut().projection_cache().insert_term(cache_key, result.clone()); |
94222f64 | 1079 | } |
ba9703b0 | 1080 | obligations.extend(result.obligations); |
f9652781 | 1081 | Ok(Some(result.value)) |
ba9703b0 | 1082 | } |
5099ac24 | 1083 | Ok(Projected::NoProgress(projected_ty)) => { |
ba9703b0 | 1084 | let result = Normalized { value: projected_ty, obligations: vec![] }; |
94222f64 | 1085 | if use_cache { |
5099ac24 | 1086 | infcx.inner.borrow_mut().projection_cache().insert_term(cache_key, result.clone()); |
94222f64 | 1087 | } |
ba9703b0 | 1088 | // No need to extend `obligations`. |
f9652781 | 1089 | Ok(Some(result.value)) |
ba9703b0 | 1090 | } |
5099ac24 | 1091 | Err(ProjectionError::TooManyCandidates) => { |
29967ef6 | 1092 | debug!("opt_normalize_projection_type: too many candidates"); |
94222f64 XL |
1093 | if use_cache { |
1094 | infcx.inner.borrow_mut().projection_cache().ambiguous(cache_key); | |
1095 | } | |
f9652781 | 1096 | Ok(None) |
ba9703b0 | 1097 | } |
5099ac24 | 1098 | Err(ProjectionError::TraitSelectionError(_)) => { |
ba9703b0 XL |
1099 | debug!("opt_normalize_projection_type: ERROR"); |
1100 | // if we got an error processing the `T as Trait` part, | |
1101 | // just return `ty::err` but add the obligation `T : | |
1102 | // Trait`, which when processed will cause the error to be | |
1103 | // reported later | |
1104 | ||
94222f64 XL |
1105 | if use_cache { |
1106 | infcx.inner.borrow_mut().projection_cache().error(cache_key); | |
1107 | } | |
ba9703b0 XL |
1108 | let result = normalize_to_error(selcx, param_env, projection_ty, cause, depth); |
1109 | obligations.extend(result.obligations); | |
5099ac24 | 1110 | Ok(Some(result.value.into())) |
ba9703b0 XL |
1111 | } |
1112 | } | |
1113 | } | |
1114 | ||
ba9703b0 XL |
1115 | /// If we are projecting `<T as Trait>::Item`, but `T: Trait` does not |
1116 | /// hold. In various error cases, we cannot generate a valid | |
1117 | /// normalized projection. Therefore, we create an inference variable | |
1118 | /// return an associated obligation that, when fulfilled, will lead to | |
1119 | /// an error. | |
1120 | /// | |
1121 | /// Note that we used to return `Error` here, but that was quite | |
1122 | /// dubious -- the premise was that an error would *eventually* be | |
1123 | /// reported, when the obligation was processed. But in general once | |
94222f64 | 1124 | /// you see an `Error` you are supposed to be able to assume that an |
ba9703b0 XL |
1125 | /// error *has been* reported, so that you can take whatever heuristic |
1126 | /// paths you want to take. To make things worse, it was possible for | |
1127 | /// cycles to arise, where you basically had a setup like `<MyType<$0> | |
1128 | /// as Trait>::Foo == $0`. Here, normalizing `<MyType<$0> as | |
1129 | /// Trait>::Foo> to `[type error]` would lead to an obligation of | |
1130 | /// `<MyType<[type error]> as Trait>::Foo`. We are supposed to report | |
1131 | /// an error for this obligation, but we legitimately should not, | |
1132 | /// because it contains `[type error]`. Yuck! (See issue #29857 for | |
1133 | /// one case where this arose.) | |
1134 | fn normalize_to_error<'a, 'tcx>( | |
1135 | selcx: &mut SelectionContext<'a, 'tcx>, | |
1136 | param_env: ty::ParamEnv<'tcx>, | |
1137 | projection_ty: ty::ProjectionTy<'tcx>, | |
1138 | cause: ObligationCause<'tcx>, | |
1139 | depth: usize, | |
1140 | ) -> NormalizedTy<'tcx> { | |
c295e0f8 | 1141 | let trait_ref = ty::Binder::dummy(projection_ty.trait_ref(selcx.tcx())); |
ba9703b0 XL |
1142 | let trait_obligation = Obligation { |
1143 | cause, | |
1144 | recursion_depth: depth, | |
1145 | param_env, | |
f9f354fc | 1146 | predicate: trait_ref.without_const().to_predicate(selcx.tcx()), |
ba9703b0 XL |
1147 | }; |
1148 | let tcx = selcx.infcx().tcx; | |
1149 | let def_id = projection_ty.item_def_id; | |
1150 | let new_value = selcx.infcx().next_ty_var(TypeVariableOrigin { | |
1151 | kind: TypeVariableOriginKind::NormalizeProjectionType, | |
1152 | span: tcx.def_span(def_id), | |
1153 | }); | |
1154 | Normalized { value: new_value, obligations: vec![trait_obligation] } | |
1155 | } | |
1156 | ||
5099ac24 | 1157 | enum Projected<'tcx> { |
ba9703b0 | 1158 | Progress(Progress<'tcx>), |
5099ac24 | 1159 | NoProgress(ty::Term<'tcx>), |
ba9703b0 XL |
1160 | } |
1161 | ||
1162 | struct Progress<'tcx> { | |
5099ac24 | 1163 | term: ty::Term<'tcx>, |
ba9703b0 XL |
1164 | obligations: Vec<PredicateObligation<'tcx>>, |
1165 | } | |
1166 | ||
1167 | impl<'tcx> Progress<'tcx> { | |
1168 | fn error(tcx: TyCtxt<'tcx>) -> Self { | |
5099ac24 | 1169 | Progress { term: tcx.ty_error().into(), obligations: vec![] } |
ba9703b0 XL |
1170 | } |
1171 | ||
1172 | fn with_addl_obligations(mut self, mut obligations: Vec<PredicateObligation<'tcx>>) -> Self { | |
ba9703b0 XL |
1173 | self.obligations.append(&mut obligations); |
1174 | self | |
1175 | } | |
1176 | } | |
1177 | ||
1178 | /// Computes the result of a projection type (if we can). | |
1179 | /// | |
1180 | /// IMPORTANT: | |
1181 | /// - `obligation` must be fully normalized | |
136023e0 | 1182 | #[tracing::instrument(level = "info", skip(selcx))] |
5099ac24 | 1183 | fn project<'cx, 'tcx>( |
ba9703b0 XL |
1184 | selcx: &mut SelectionContext<'cx, 'tcx>, |
1185 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1186 | ) -> Result<Projected<'tcx>, ProjectionError<'tcx>> { |
136023e0 | 1187 | if !selcx.tcx().recursion_limit().value_within_limit(obligation.recursion_depth) { |
fc512014 XL |
1188 | // This should really be an immediate error, but some existing code |
1189 | // relies on being able to recover from this. | |
ee023bcb FG |
1190 | return Err(ProjectionError::TraitSelectionError(SelectionError::Overflow( |
1191 | OverflowError::Canonical, | |
1192 | ))); | |
ba9703b0 XL |
1193 | } |
1194 | ||
6a06907d | 1195 | if obligation.predicate.references_error() { |
5099ac24 | 1196 | return Ok(Projected::Progress(Progress::error(selcx.tcx()))); |
ba9703b0 XL |
1197 | } |
1198 | ||
5099ac24 | 1199 | let mut candidates = ProjectionCandidateSet::None; |
ba9703b0 XL |
1200 | |
1201 | // Make sure that the following procedures are kept in order. ParamEnv | |
1202 | // needs to be first because it has highest priority, and Select checks | |
1203 | // the return value of push_candidate which assumes it's ran at last. | |
6a06907d | 1204 | assemble_candidates_from_param_env(selcx, obligation, &mut candidates); |
ba9703b0 | 1205 | |
6a06907d | 1206 | assemble_candidates_from_trait_def(selcx, obligation, &mut candidates); |
ba9703b0 | 1207 | |
6a06907d | 1208 | assemble_candidates_from_object_ty(selcx, obligation, &mut candidates); |
29967ef6 | 1209 | |
5099ac24 | 1210 | if let ProjectionCandidateSet::Single(ProjectionCandidate::Object(_)) = candidates { |
29967ef6 XL |
1211 | // Avoid normalization cycle from selection (see |
1212 | // `assemble_candidates_from_object_ty`). | |
1213 | // FIXME(lazy_normalization): Lazy normalization should save us from | |
6a06907d | 1214 | // having to special case this. |
29967ef6 | 1215 | } else { |
6a06907d | 1216 | assemble_candidates_from_impls(selcx, obligation, &mut candidates); |
29967ef6 | 1217 | }; |
ba9703b0 XL |
1218 | |
1219 | match candidates { | |
5099ac24 FG |
1220 | ProjectionCandidateSet::Single(candidate) => { |
1221 | Ok(Projected::Progress(confirm_candidate(selcx, obligation, candidate))) | |
29967ef6 | 1222 | } |
5099ac24 FG |
1223 | ProjectionCandidateSet::None => Ok(Projected::NoProgress( |
1224 | // FIXME(associated_const_generics): this may need to change in the future? | |
1225 | // need to investigate whether or not this is fine. | |
ba9703b0 XL |
1226 | selcx |
1227 | .tcx() | |
5099ac24 FG |
1228 | .mk_projection(obligation.predicate.item_def_id, obligation.predicate.substs) |
1229 | .into(), | |
ba9703b0 XL |
1230 | )), |
1231 | // Error occurred while trying to processing impls. | |
5099ac24 | 1232 | ProjectionCandidateSet::Error(e) => Err(ProjectionError::TraitSelectionError(e)), |
ba9703b0 XL |
1233 | // Inherent ambiguity that prevents us from even enumerating the |
1234 | // candidates. | |
5099ac24 | 1235 | ProjectionCandidateSet::Ambiguous => Err(ProjectionError::TooManyCandidates), |
ba9703b0 XL |
1236 | } |
1237 | } | |
1238 | ||
1239 | /// The first thing we have to do is scan through the parameter | |
1240 | /// environment to see whether there are any projection predicates | |
1241 | /// there that can answer this question. | |
1242 | fn assemble_candidates_from_param_env<'cx, 'tcx>( | |
1243 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1244 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1245 | candidate_set: &mut ProjectionCandidateSet<'tcx>, |
ba9703b0 | 1246 | ) { |
ba9703b0 XL |
1247 | assemble_candidates_from_predicates( |
1248 | selcx, | |
1249 | obligation, | |
ba9703b0 | 1250 | candidate_set, |
5099ac24 | 1251 | ProjectionCandidate::ParamEnv, |
f035d41b | 1252 | obligation.param_env.caller_bounds().iter(), |
29967ef6 | 1253 | false, |
ba9703b0 XL |
1254 | ); |
1255 | } | |
1256 | ||
1257 | /// In the case of a nested projection like <<A as Foo>::FooT as Bar>::BarT, we may find | |
1258 | /// that the definition of `Foo` has some clues: | |
1259 | /// | |
1260 | /// ``` | |
1261 | /// trait Foo { | |
1262 | /// type FooT : Bar<BarT=i32> | |
1263 | /// } | |
1264 | /// ``` | |
1265 | /// | |
1266 | /// Here, for example, we could conclude that the result is `i32`. | |
1267 | fn assemble_candidates_from_trait_def<'cx, 'tcx>( | |
1268 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1269 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1270 | candidate_set: &mut ProjectionCandidateSet<'tcx>, |
ba9703b0 XL |
1271 | ) { |
1272 | debug!("assemble_candidates_from_trait_def(..)"); | |
1273 | ||
1274 | let tcx = selcx.tcx(); | |
1275 | // Check whether the self-type is itself a projection. | |
f035d41b | 1276 | // If so, extract what we know from the trait and try to come up with a good answer. |
6a06907d | 1277 | let bounds = match *obligation.predicate.self_ty().kind() { |
29967ef6 XL |
1278 | ty::Projection(ref data) => tcx.item_bounds(data.item_def_id).subst(tcx, data.substs), |
1279 | ty::Opaque(def_id, substs) => tcx.item_bounds(def_id).subst(tcx, substs), | |
ba9703b0 XL |
1280 | ty::Infer(ty::TyVar(_)) => { |
1281 | // If the self-type is an inference variable, then it MAY wind up | |
1282 | // being a projected type, so induce an ambiguity. | |
1283 | candidate_set.mark_ambiguous(); | |
1284 | return; | |
1285 | } | |
1286 | _ => return, | |
1287 | }; | |
1288 | ||
ba9703b0 XL |
1289 | assemble_candidates_from_predicates( |
1290 | selcx, | |
1291 | obligation, | |
ba9703b0 | 1292 | candidate_set, |
5099ac24 | 1293 | ProjectionCandidate::TraitDef, |
f035d41b | 1294 | bounds.iter(), |
29967ef6 | 1295 | true, |
5099ac24 | 1296 | ); |
ba9703b0 XL |
1297 | } |
1298 | ||
29967ef6 XL |
1299 | /// In the case of a trait object like |
1300 | /// `<dyn Iterator<Item = ()> as Iterator>::Item` we can use the existential | |
1301 | /// predicate in the trait object. | |
1302 | /// | |
1303 | /// We don't go through the select candidate for these bounds to avoid cycles: | |
1304 | /// In the above case, `dyn Iterator<Item = ()>: Iterator` would create a | |
1305 | /// nested obligation of `<dyn Iterator<Item = ()> as Iterator>::Item: Sized`, | |
1306 | /// this then has to be normalized without having to prove | |
1307 | /// `dyn Iterator<Item = ()>: Iterator` again. | |
1308 | fn assemble_candidates_from_object_ty<'cx, 'tcx>( | |
1309 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1310 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1311 | candidate_set: &mut ProjectionCandidateSet<'tcx>, |
29967ef6 XL |
1312 | ) { |
1313 | debug!("assemble_candidates_from_object_ty(..)"); | |
1314 | ||
1315 | let tcx = selcx.tcx(); | |
1316 | ||
6a06907d | 1317 | let self_ty = obligation.predicate.self_ty(); |
29967ef6 XL |
1318 | let object_ty = selcx.infcx().shallow_resolve(self_ty); |
1319 | let data = match object_ty.kind() { | |
1320 | ty::Dynamic(data, ..) => data, | |
1321 | ty::Infer(ty::TyVar(_)) => { | |
1322 | // If the self-type is an inference variable, then it MAY wind up | |
1323 | // being an object type, so induce an ambiguity. | |
1324 | candidate_set.mark_ambiguous(); | |
1325 | return; | |
1326 | } | |
1327 | _ => return, | |
1328 | }; | |
1329 | let env_predicates = data | |
1330 | .projection_bounds() | |
1331 | .filter(|bound| bound.item_def_id() == obligation.predicate.item_def_id) | |
1332 | .map(|p| p.with_self_ty(tcx, object_ty).to_predicate(tcx)); | |
1333 | ||
1334 | assemble_candidates_from_predicates( | |
1335 | selcx, | |
1336 | obligation, | |
29967ef6 | 1337 | candidate_set, |
5099ac24 | 1338 | ProjectionCandidate::Object, |
29967ef6 XL |
1339 | env_predicates, |
1340 | false, | |
1341 | ); | |
1342 | } | |
1343 | ||
5099ac24 FG |
1344 | #[tracing::instrument( |
1345 | level = "debug", | |
1346 | skip(selcx, candidate_set, ctor, env_predicates, potentially_unnormalized_candidates) | |
1347 | )] | |
ba9703b0 XL |
1348 | fn assemble_candidates_from_predicates<'cx, 'tcx>( |
1349 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1350 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 FG |
1351 | candidate_set: &mut ProjectionCandidateSet<'tcx>, |
1352 | ctor: fn(ty::PolyProjectionPredicate<'tcx>) -> ProjectionCandidate<'tcx>, | |
ba9703b0 | 1353 | env_predicates: impl Iterator<Item = ty::Predicate<'tcx>>, |
29967ef6 | 1354 | potentially_unnormalized_candidates: bool, |
ba9703b0 | 1355 | ) { |
ba9703b0 XL |
1356 | let infcx = selcx.infcx(); |
1357 | for predicate in env_predicates { | |
5869c6ff XL |
1358 | let bound_predicate = predicate.kind(); |
1359 | if let ty::PredicateKind::Projection(data) = predicate.kind().skip_binder() { | |
29967ef6 | 1360 | let data = bound_predicate.rebind(data); |
5099ac24 FG |
1361 | if data.projection_def_id() != obligation.predicate.item_def_id { |
1362 | continue; | |
1363 | } | |
ba9703b0 | 1364 | |
5099ac24 FG |
1365 | let is_match = infcx.probe(|_| { |
1366 | selcx.match_projection_projections( | |
1367 | obligation, | |
1368 | data, | |
1369 | potentially_unnormalized_candidates, | |
1370 | ) | |
1371 | }); | |
29967ef6 | 1372 | |
5099ac24 FG |
1373 | match is_match { |
1374 | ProjectionMatchesProjection::Yes => { | |
1375 | candidate_set.push_candidate(ctor(data)); | |
1376 | ||
1377 | if potentially_unnormalized_candidates | |
1378 | && !obligation.predicate.has_infer_types_or_consts() | |
1379 | { | |
1380 | // HACK: Pick the first trait def candidate for a fully | |
1381 | // inferred predicate. This is to allow duplicates that | |
1382 | // differ only in normalization. | |
1383 | return; | |
1384 | } | |
1385 | } | |
1386 | ProjectionMatchesProjection::Ambiguous => { | |
1387 | candidate_set.mark_ambiguous(); | |
29967ef6 | 1388 | } |
5099ac24 | 1389 | ProjectionMatchesProjection::No => {} |
ba9703b0 XL |
1390 | } |
1391 | } | |
1392 | } | |
1393 | } | |
1394 | ||
5099ac24 | 1395 | #[tracing::instrument(level = "debug", skip(selcx, obligation, candidate_set))] |
ba9703b0 XL |
1396 | fn assemble_candidates_from_impls<'cx, 'tcx>( |
1397 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1398 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1399 | candidate_set: &mut ProjectionCandidateSet<'tcx>, |
ba9703b0 XL |
1400 | ) { |
1401 | // If we are resolving `<T as TraitRef<...>>::Item == Type`, | |
1402 | // start out by selecting the predicate `T as TraitRef<...>`: | |
c295e0f8 | 1403 | let poly_trait_ref = ty::Binder::dummy(obligation.predicate.trait_ref(selcx.tcx())); |
ba9703b0 XL |
1404 | let trait_obligation = obligation.with(poly_trait_ref.to_poly_trait_predicate()); |
1405 | let _ = selcx.infcx().commit_if_ok(|_| { | |
f035d41b XL |
1406 | let impl_source = match selcx.select(&trait_obligation) { |
1407 | Ok(Some(impl_source)) => impl_source, | |
ba9703b0 XL |
1408 | Ok(None) => { |
1409 | candidate_set.mark_ambiguous(); | |
1410 | return Err(()); | |
1411 | } | |
1412 | Err(e) => { | |
29967ef6 | 1413 | debug!(error = ?e, "selection error"); |
ba9703b0 XL |
1414 | candidate_set.mark_error(e); |
1415 | return Err(()); | |
1416 | } | |
1417 | }; | |
1418 | ||
f035d41b | 1419 | let eligible = match &impl_source { |
1b1a35ee XL |
1420 | super::ImplSource::Closure(_) |
1421 | | super::ImplSource::Generator(_) | |
1422 | | super::ImplSource::FnPointer(_) | |
5099ac24 | 1423 | | super::ImplSource::TraitAlias(_) => true, |
1b1a35ee | 1424 | super::ImplSource::UserDefined(impl_data) => { |
ba9703b0 XL |
1425 | // We have to be careful when projecting out of an |
1426 | // impl because of specialization. If we are not in | |
1427 | // codegen (i.e., projection mode is not "any"), and the | |
1428 | // impl's type is declared as default, then we disable | |
1429 | // projection (even if the trait ref is fully | |
1430 | // monomorphic). In the case where trait ref is not | |
1431 | // fully monomorphic (i.e., includes type parameters), | |
1432 | // this is because those type parameters may | |
1433 | // ultimately be bound to types from other crates that | |
1434 | // may have specialized impls we can't see. In the | |
1435 | // case where the trait ref IS fully monomorphic, this | |
1436 | // is a policy decision that we made in the RFC in | |
1437 | // order to preserve flexibility for the crate that | |
1438 | // defined the specializable impl to specialize later | |
1439 | // for existing types. | |
1440 | // | |
1441 | // In either case, we handle this by not adding a | |
1442 | // candidate for an impl if it contains a `default` | |
1443 | // type. | |
1444 | // | |
1445 | // NOTE: This should be kept in sync with the similar code in | |
fc512014 | 1446 | // `rustc_ty_utils::instance::resolve_associated_item()`. |
ba9703b0 | 1447 | let node_item = |
5099ac24 | 1448 | assoc_def(selcx, impl_data.impl_def_id, obligation.predicate.item_def_id) |
ee023bcb | 1449 | .map_err(|ErrorGuaranteed { .. }| ())?; |
ba9703b0 XL |
1450 | |
1451 | if node_item.is_final() { | |
1452 | // Non-specializable items are always projectable. | |
1453 | true | |
1454 | } else { | |
1455 | // Only reveal a specializable default if we're past type-checking | |
1456 | // and the obligation is monomorphic, otherwise passes such as | |
1457 | // transmute checking and polymorphic MIR optimizations could | |
1458 | // get a result which isn't correct for all monomorphizations. | |
f035d41b | 1459 | if obligation.param_env.reveal() == Reveal::All { |
ba9703b0 XL |
1460 | // NOTE(eddyb) inference variables can resolve to parameters, so |
1461 | // assume `poly_trait_ref` isn't monomorphic, if it contains any. | |
fc512014 | 1462 | let poly_trait_ref = selcx.infcx().resolve_vars_if_possible(poly_trait_ref); |
ba9703b0 XL |
1463 | !poly_trait_ref.still_further_specializable() |
1464 | } else { | |
1465 | debug!( | |
29967ef6 XL |
1466 | assoc_ty = ?selcx.tcx().def_path_str(node_item.item.def_id), |
1467 | ?obligation.predicate, | |
1468 | "assemble_candidates_from_impls: not eligible due to default", | |
ba9703b0 XL |
1469 | ); |
1470 | false | |
1471 | } | |
1472 | } | |
1473 | } | |
1b1a35ee | 1474 | super::ImplSource::DiscriminantKind(..) => { |
f9f354fc XL |
1475 | // While `DiscriminantKind` is automatically implemented for every type, |
1476 | // the concrete discriminant may not be known yet. | |
1477 | // | |
1478 | // Any type with multiple potential discriminant types is therefore not eligible. | |
1479 | let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); | |
1480 | ||
1b1a35ee | 1481 | match self_ty.kind() { |
f9f354fc XL |
1482 | ty::Bool |
1483 | | ty::Char | |
1484 | | ty::Int(_) | |
1485 | | ty::Uint(_) | |
1486 | | ty::Float(_) | |
1487 | | ty::Adt(..) | |
1488 | | ty::Foreign(_) | |
1489 | | ty::Str | |
1490 | | ty::Array(..) | |
1491 | | ty::Slice(_) | |
1492 | | ty::RawPtr(..) | |
1493 | | ty::Ref(..) | |
1494 | | ty::FnDef(..) | |
1495 | | ty::FnPtr(..) | |
1496 | | ty::Dynamic(..) | |
1497 | | ty::Closure(..) | |
1498 | | ty::Generator(..) | |
1499 | | ty::GeneratorWitness(..) | |
1500 | | ty::Never | |
1501 | | ty::Tuple(..) | |
1502 | // Integers and floats always have `u8` as their discriminant. | |
1503 | | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, | |
1504 | ||
1505 | ty::Projection(..) | |
1506 | | ty::Opaque(..) | |
1507 | | ty::Param(..) | |
1508 | | ty::Bound(..) | |
1509 | | ty::Placeholder(..) | |
1510 | | ty::Infer(..) | |
f035d41b | 1511 | | ty::Error(_) => false, |
f9f354fc XL |
1512 | } |
1513 | } | |
6a06907d XL |
1514 | super::ImplSource::Pointee(..) => { |
1515 | // While `Pointee` is automatically implemented for every type, | |
1516 | // the concrete metadata type may not be known yet. | |
1517 | // | |
1518 | // Any type with multiple potential metadata types is therefore not eligible. | |
1519 | let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); | |
1520 | ||
5099ac24 | 1521 | let tail = selcx.tcx().struct_tail_with_normalize(self_ty, |ty| { |
ee023bcb FG |
1522 | // We throw away any obligations we get from this, since we normalize |
1523 | // and confirm these obligations once again during confirmation | |
5099ac24 FG |
1524 | normalize_with_depth( |
1525 | selcx, | |
1526 | obligation.param_env, | |
1527 | obligation.cause.clone(), | |
1528 | obligation.recursion_depth + 1, | |
1529 | ty, | |
1530 | ) | |
1531 | .value | |
1532 | }); | |
1533 | ||
6a06907d XL |
1534 | match tail.kind() { |
1535 | ty::Bool | |
1536 | | ty::Char | |
1537 | | ty::Int(_) | |
1538 | | ty::Uint(_) | |
1539 | | ty::Float(_) | |
6a06907d XL |
1540 | | ty::Str |
1541 | | ty::Array(..) | |
1542 | | ty::Slice(_) | |
1543 | | ty::RawPtr(..) | |
1544 | | ty::Ref(..) | |
1545 | | ty::FnDef(..) | |
1546 | | ty::FnPtr(..) | |
1547 | | ty::Dynamic(..) | |
1548 | | ty::Closure(..) | |
1549 | | ty::Generator(..) | |
1550 | | ty::GeneratorWitness(..) | |
1551 | | ty::Never | |
ee023bcb FG |
1552 | // Extern types have unit metadata, according to RFC 2850 |
1553 | | ty::Foreign(_) | |
6a06907d XL |
1554 | // If returned by `struct_tail_without_normalization` this is a unit struct |
1555 | // without any fields, or not a struct, and therefore is Sized. | |
1556 | | ty::Adt(..) | |
1557 | // If returned by `struct_tail_without_normalization` this is the empty tuple. | |
1558 | | ty::Tuple(..) | |
1559 | // Integers and floats are always Sized, and so have unit type metadata. | |
1560 | | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true, | |
1561 | ||
ee023bcb FG |
1562 | // type parameters, opaques, and unnormalized projections have pointer |
1563 | // metadata if they're known (e.g. by the param_env) to be sized | |
1564 | ty::Param(_) | ty::Projection(..) | ty::Opaque(..) | |
1565 | if tail.is_sized(selcx.tcx().at(obligation.cause.span), obligation.param_env) => | |
1566 | { | |
1567 | true | |
1568 | } | |
1569 | ||
1570 | // FIXME(compiler-errors): are Bound and Placeholder types ever known sized? | |
1571 | ty::Param(_) | |
1572 | | ty::Projection(..) | |
6a06907d | 1573 | | ty::Opaque(..) |
6a06907d XL |
1574 | | ty::Bound(..) |
1575 | | ty::Placeholder(..) | |
1576 | | ty::Infer(..) | |
5099ac24 FG |
1577 | | ty::Error(_) => { |
1578 | if tail.has_infer_types() { | |
1579 | candidate_set.mark_ambiguous(); | |
1580 | } | |
1581 | false | |
ee023bcb | 1582 | } |
6a06907d XL |
1583 | } |
1584 | } | |
1b1a35ee | 1585 | super::ImplSource::Param(..) => { |
ba9703b0 XL |
1586 | // This case tell us nothing about the value of an |
1587 | // associated type. Consider: | |
1588 | // | |
1589 | // ``` | |
1590 | // trait SomeTrait { type Foo; } | |
1591 | // fn foo<T:SomeTrait>(...) { } | |
1592 | // ``` | |
1593 | // | |
1594 | // If the user writes `<T as SomeTrait>::Foo`, then the `T | |
1595 | // : SomeTrait` binding does not help us decide what the | |
1596 | // type `Foo` is (at least, not more specifically than | |
1597 | // what we already knew). | |
1598 | // | |
1599 | // But wait, you say! What about an example like this: | |
1600 | // | |
1601 | // ``` | |
1602 | // fn bar<T:SomeTrait<Foo=usize>>(...) { ... } | |
1603 | // ``` | |
1604 | // | |
ee023bcb | 1605 | // Doesn't the `T : SomeTrait<Foo=usize>` predicate help |
ba9703b0 XL |
1606 | // resolve `T::Foo`? And of course it does, but in fact |
1607 | // that single predicate is desugared into two predicates | |
1608 | // in the compiler: a trait predicate (`T : SomeTrait`) and a | |
1609 | // projection. And the projection where clause is handled | |
1610 | // in `assemble_candidates_from_param_env`. | |
1611 | false | |
1612 | } | |
29967ef6 XL |
1613 | super::ImplSource::Object(_) => { |
1614 | // Handled by the `Object` projection candidate. See | |
1615 | // `assemble_candidates_from_object_ty` for an explanation of | |
1616 | // why we special case object types. | |
1617 | false | |
1618 | } | |
94222f64 XL |
1619 | super::ImplSource::AutoImpl(..) |
1620 | | super::ImplSource::Builtin(..) | |
c295e0f8 | 1621 | | super::ImplSource::TraitUpcasting(_) |
ee023bcb | 1622 | | super::ImplSource::ConstDestruct(_) => { |
ba9703b0 | 1623 | // These traits have no associated types. |
f9652781 | 1624 | selcx.tcx().sess.delay_span_bug( |
ba9703b0 | 1625 | obligation.cause.span, |
f9652781 | 1626 | &format!("Cannot project an associated type from `{:?}`", impl_source), |
ba9703b0 | 1627 | ); |
f9652781 | 1628 | return Err(()); |
ba9703b0 XL |
1629 | } |
1630 | }; | |
1631 | ||
1632 | if eligible { | |
5099ac24 | 1633 | if candidate_set.push_candidate(ProjectionCandidate::Select(impl_source)) { |
ba9703b0 XL |
1634 | Ok(()) |
1635 | } else { | |
1636 | Err(()) | |
1637 | } | |
1638 | } else { | |
1639 | Err(()) | |
1640 | } | |
1641 | }); | |
1642 | } | |
1643 | ||
1644 | fn confirm_candidate<'cx, 'tcx>( | |
1645 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1646 | obligation: &ProjectionTyObligation<'tcx>, | |
5099ac24 | 1647 | candidate: ProjectionCandidate<'tcx>, |
ba9703b0 | 1648 | ) -> Progress<'tcx> { |
29967ef6 | 1649 | debug!(?obligation, ?candidate, "confirm_candidate"); |
f035d41b | 1650 | let mut progress = match candidate { |
5099ac24 FG |
1651 | ProjectionCandidate::ParamEnv(poly_projection) |
1652 | | ProjectionCandidate::Object(poly_projection) => { | |
29967ef6 XL |
1653 | confirm_param_env_candidate(selcx, obligation, poly_projection, false) |
1654 | } | |
1655 | ||
5099ac24 | 1656 | ProjectionCandidate::TraitDef(poly_projection) => { |
29967ef6 | 1657 | confirm_param_env_candidate(selcx, obligation, poly_projection, true) |
ba9703b0 XL |
1658 | } |
1659 | ||
5099ac24 | 1660 | ProjectionCandidate::Select(impl_source) => { |
29967ef6 | 1661 | confirm_select_candidate(selcx, obligation, impl_source) |
ba9703b0 | 1662 | } |
f035d41b | 1663 | }; |
5099ac24 | 1664 | |
f035d41b XL |
1665 | // When checking for cycle during evaluation, we compare predicates with |
1666 | // "syntactic" equality. Since normalization generally introduces a type | |
1667 | // with new region variables, we need to resolve them to existing variables | |
1668 | // when possible for this to work. See `auto-trait-projection-recursion.rs` | |
1669 | // for a case where this matters. | |
5099ac24 FG |
1670 | if progress.term.has_infer_regions() { |
1671 | progress.term = | |
1672 | progress.term.fold_with(&mut OpportunisticRegionResolver::new(selcx.infcx())); | |
ba9703b0 | 1673 | } |
f035d41b | 1674 | progress |
ba9703b0 XL |
1675 | } |
1676 | ||
1677 | fn confirm_select_candidate<'cx, 'tcx>( | |
1678 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1679 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1680 | impl_source: Selection<'tcx>, |
ba9703b0 | 1681 | ) -> Progress<'tcx> { |
f035d41b | 1682 | match impl_source { |
1b1a35ee XL |
1683 | super::ImplSource::UserDefined(data) => confirm_impl_candidate(selcx, obligation, data), |
1684 | super::ImplSource::Generator(data) => confirm_generator_candidate(selcx, obligation, data), | |
1685 | super::ImplSource::Closure(data) => confirm_closure_candidate(selcx, obligation, data), | |
1686 | super::ImplSource::FnPointer(data) => confirm_fn_pointer_candidate(selcx, obligation, data), | |
1687 | super::ImplSource::DiscriminantKind(data) => { | |
f9f354fc XL |
1688 | confirm_discriminant_kind_candidate(selcx, obligation, data) |
1689 | } | |
6a06907d | 1690 | super::ImplSource::Pointee(data) => confirm_pointee_candidate(selcx, obligation, data), |
29967ef6 XL |
1691 | super::ImplSource::Object(_) |
1692 | | super::ImplSource::AutoImpl(..) | |
1b1a35ee XL |
1693 | | super::ImplSource::Param(..) |
1694 | | super::ImplSource::Builtin(..) | |
94222f64 | 1695 | | super::ImplSource::TraitUpcasting(_) |
c295e0f8 | 1696 | | super::ImplSource::TraitAlias(..) |
ee023bcb | 1697 | | super::ImplSource::ConstDestruct(_) => { |
29967ef6 | 1698 | // we don't create Select candidates with this kind of resolution |
ba9703b0 XL |
1699 | span_bug!( |
1700 | obligation.cause.span, | |
1701 | "Cannot project an associated type from `{:?}`", | |
f035d41b | 1702 | impl_source |
ba9703b0 XL |
1703 | ) |
1704 | } | |
1705 | } | |
1706 | } | |
1707 | ||
ba9703b0 XL |
1708 | fn confirm_generator_candidate<'cx, 'tcx>( |
1709 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1710 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1711 | impl_source: ImplSourceGeneratorData<'tcx, PredicateObligation<'tcx>>, |
ba9703b0 | 1712 | ) -> Progress<'tcx> { |
f035d41b | 1713 | let gen_sig = impl_source.substs.as_generator().poly_sig(); |
ba9703b0 XL |
1714 | let Normalized { value: gen_sig, obligations } = normalize_with_depth( |
1715 | selcx, | |
1716 | obligation.param_env, | |
1717 | obligation.cause.clone(), | |
1718 | obligation.recursion_depth + 1, | |
fc512014 | 1719 | gen_sig, |
ba9703b0 XL |
1720 | ); |
1721 | ||
29967ef6 | 1722 | debug!(?obligation, ?gen_sig, ?obligations, "confirm_generator_candidate"); |
ba9703b0 XL |
1723 | |
1724 | let tcx = selcx.tcx(); | |
1725 | ||
3dfed10e | 1726 | let gen_def_id = tcx.require_lang_item(LangItem::Generator, None); |
ba9703b0 XL |
1727 | |
1728 | let predicate = super::util::generator_trait_ref_and_outputs( | |
1729 | tcx, | |
1730 | gen_def_id, | |
1731 | obligation.predicate.self_ty(), | |
1732 | gen_sig, | |
1733 | ) | |
1734 | .map_bound(|(trait_ref, yield_ty, return_ty)| { | |
5099ac24 | 1735 | let name = tcx.associated_item(obligation.predicate.item_def_id).name; |
ba9703b0 XL |
1736 | let ty = if name == sym::Return { |
1737 | return_ty | |
1738 | } else if name == sym::Yield { | |
1739 | yield_ty | |
1740 | } else { | |
1741 | bug!() | |
1742 | }; | |
1743 | ||
1744 | ty::ProjectionPredicate { | |
1745 | projection_ty: ty::ProjectionTy { | |
1746 | substs: trait_ref.substs, | |
1747 | item_def_id: obligation.predicate.item_def_id, | |
1748 | }, | |
5099ac24 | 1749 | term: ty.into(), |
ba9703b0 XL |
1750 | } |
1751 | }); | |
1752 | ||
29967ef6 | 1753 | confirm_param_env_candidate(selcx, obligation, predicate, false) |
f035d41b | 1754 | .with_addl_obligations(impl_source.nested) |
ba9703b0 XL |
1755 | .with_addl_obligations(obligations) |
1756 | } | |
1757 | ||
f9f354fc XL |
1758 | fn confirm_discriminant_kind_candidate<'cx, 'tcx>( |
1759 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1760 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1761 | _: ImplSourceDiscriminantKindData, |
f9f354fc XL |
1762 | ) -> Progress<'tcx> { |
1763 | let tcx = selcx.tcx(); | |
1764 | ||
1765 | let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); | |
cdc7bbd5 XL |
1766 | // We get here from `poly_project_and_unify_type` which replaces bound vars |
1767 | // with placeholders | |
1768 | debug_assert!(!self_ty.has_escaping_bound_vars()); | |
f9f354fc XL |
1769 | let substs = tcx.mk_substs([self_ty.into()].iter()); |
1770 | ||
3dfed10e | 1771 | let discriminant_def_id = tcx.require_lang_item(LangItem::Discriminant, None); |
f9f354fc XL |
1772 | |
1773 | let predicate = ty::ProjectionPredicate { | |
1774 | projection_ty: ty::ProjectionTy { substs, item_def_id: discriminant_def_id }, | |
5099ac24 | 1775 | term: self_ty.discriminant_ty(tcx).into(), |
f9f354fc XL |
1776 | }; |
1777 | ||
fc512014 XL |
1778 | // We get here from `poly_project_and_unify_type` which replaces bound vars |
1779 | // with placeholders, so dummy is okay here. | |
1780 | confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false) | |
f9f354fc XL |
1781 | } |
1782 | ||
6a06907d XL |
1783 | fn confirm_pointee_candidate<'cx, 'tcx>( |
1784 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1785 | obligation: &ProjectionTyObligation<'tcx>, | |
1786 | _: ImplSourcePointeeData, | |
1787 | ) -> Progress<'tcx> { | |
1788 | let tcx = selcx.tcx(); | |
6a06907d | 1789 | let self_ty = selcx.infcx().shallow_resolve(obligation.predicate.self_ty()); |
6a06907d | 1790 | |
5099ac24 | 1791 | let mut obligations = vec![]; |
ee023bcb | 1792 | let (metadata_ty, check_is_sized) = self_ty.ptr_metadata_ty(tcx, |ty| { |
5099ac24 FG |
1793 | normalize_with_depth_to( |
1794 | selcx, | |
1795 | obligation.param_env, | |
1796 | obligation.cause.clone(), | |
1797 | obligation.recursion_depth + 1, | |
1798 | ty, | |
1799 | &mut obligations, | |
1800 | ) | |
1801 | }); | |
ee023bcb FG |
1802 | if check_is_sized { |
1803 | let sized_predicate = ty::Binder::dummy(ty::TraitRef::new( | |
1804 | tcx.require_lang_item(LangItem::Sized, None), | |
1805 | tcx.mk_substs_trait(self_ty, &[]), | |
1806 | )) | |
1807 | .without_const() | |
1808 | .to_predicate(tcx); | |
1809 | obligations.push(Obligation::new( | |
1810 | obligation.cause.clone(), | |
1811 | obligation.param_env, | |
1812 | sized_predicate, | |
1813 | )); | |
1814 | } | |
5099ac24 FG |
1815 | |
1816 | let substs = tcx.mk_substs([self_ty.into()].iter()); | |
6a06907d XL |
1817 | let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None); |
1818 | ||
1819 | let predicate = ty::ProjectionPredicate { | |
1820 | projection_ty: ty::ProjectionTy { substs, item_def_id: metadata_def_id }, | |
5099ac24 | 1821 | term: metadata_ty.into(), |
6a06907d XL |
1822 | }; |
1823 | ||
136023e0 | 1824 | confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false) |
5099ac24 | 1825 | .with_addl_obligations(obligations) |
6a06907d XL |
1826 | } |
1827 | ||
ba9703b0 XL |
1828 | fn confirm_fn_pointer_candidate<'cx, 'tcx>( |
1829 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1830 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1831 | fn_pointer_impl_source: ImplSourceFnPointerData<'tcx, PredicateObligation<'tcx>>, |
ba9703b0 | 1832 | ) -> Progress<'tcx> { |
f035d41b | 1833 | let fn_type = selcx.infcx().shallow_resolve(fn_pointer_impl_source.fn_ty); |
ba9703b0 XL |
1834 | let sig = fn_type.fn_sig(selcx.tcx()); |
1835 | let Normalized { value: sig, obligations } = normalize_with_depth( | |
1836 | selcx, | |
1837 | obligation.param_env, | |
1838 | obligation.cause.clone(), | |
1839 | obligation.recursion_depth + 1, | |
fc512014 | 1840 | sig, |
ba9703b0 XL |
1841 | ); |
1842 | ||
1843 | confirm_callable_candidate(selcx, obligation, sig, util::TupleArgumentsFlag::Yes) | |
f035d41b | 1844 | .with_addl_obligations(fn_pointer_impl_source.nested) |
ba9703b0 XL |
1845 | .with_addl_obligations(obligations) |
1846 | } | |
1847 | ||
1848 | fn confirm_closure_candidate<'cx, 'tcx>( | |
1849 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1850 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1851 | impl_source: ImplSourceClosureData<'tcx, PredicateObligation<'tcx>>, |
ba9703b0 | 1852 | ) -> Progress<'tcx> { |
f035d41b | 1853 | let closure_sig = impl_source.substs.as_closure().sig(); |
ba9703b0 XL |
1854 | let Normalized { value: closure_sig, obligations } = normalize_with_depth( |
1855 | selcx, | |
1856 | obligation.param_env, | |
1857 | obligation.cause.clone(), | |
1858 | obligation.recursion_depth + 1, | |
fc512014 | 1859 | closure_sig, |
ba9703b0 XL |
1860 | ); |
1861 | ||
29967ef6 | 1862 | debug!(?obligation, ?closure_sig, ?obligations, "confirm_closure_candidate"); |
ba9703b0 XL |
1863 | |
1864 | confirm_callable_candidate(selcx, obligation, closure_sig, util::TupleArgumentsFlag::No) | |
f035d41b | 1865 | .with_addl_obligations(impl_source.nested) |
ba9703b0 XL |
1866 | .with_addl_obligations(obligations) |
1867 | } | |
1868 | ||
1869 | fn confirm_callable_candidate<'cx, 'tcx>( | |
1870 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1871 | obligation: &ProjectionTyObligation<'tcx>, | |
1872 | fn_sig: ty::PolyFnSig<'tcx>, | |
1873 | flag: util::TupleArgumentsFlag, | |
1874 | ) -> Progress<'tcx> { | |
1875 | let tcx = selcx.tcx(); | |
1876 | ||
29967ef6 | 1877 | debug!(?obligation, ?fn_sig, "confirm_callable_candidate"); |
ba9703b0 | 1878 | |
3dfed10e XL |
1879 | let fn_once_def_id = tcx.require_lang_item(LangItem::FnOnce, None); |
1880 | let fn_once_output_def_id = tcx.require_lang_item(LangItem::FnOnceOutput, None); | |
ba9703b0 XL |
1881 | |
1882 | let predicate = super::util::closure_trait_ref_and_return_type( | |
1883 | tcx, | |
1884 | fn_once_def_id, | |
1885 | obligation.predicate.self_ty(), | |
1886 | fn_sig, | |
1887 | flag, | |
1888 | ) | |
1889 | .map_bound(|(trait_ref, ret_type)| ty::ProjectionPredicate { | |
f035d41b XL |
1890 | projection_ty: ty::ProjectionTy { |
1891 | substs: trait_ref.substs, | |
1892 | item_def_id: fn_once_output_def_id, | |
1893 | }, | |
5099ac24 | 1894 | term: ret_type.into(), |
ba9703b0 XL |
1895 | }); |
1896 | ||
3c0e092e | 1897 | confirm_param_env_candidate(selcx, obligation, predicate, true) |
ba9703b0 XL |
1898 | } |
1899 | ||
1900 | fn confirm_param_env_candidate<'cx, 'tcx>( | |
1901 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1902 | obligation: &ProjectionTyObligation<'tcx>, | |
1903 | poly_cache_entry: ty::PolyProjectionPredicate<'tcx>, | |
29967ef6 | 1904 | potentially_unnormalized_candidate: bool, |
ba9703b0 XL |
1905 | ) -> Progress<'tcx> { |
1906 | let infcx = selcx.infcx(); | |
1907 | let cause = &obligation.cause; | |
1908 | let param_env = obligation.param_env; | |
1909 | ||
1910 | let (cache_entry, _) = infcx.replace_bound_vars_with_fresh_vars( | |
1911 | cause.span, | |
1912 | LateBoundRegionConversionTime::HigherRankedType, | |
fc512014 | 1913 | poly_cache_entry, |
ba9703b0 XL |
1914 | ); |
1915 | ||
6a06907d | 1916 | let cache_projection = cache_entry.projection_ty; |
29967ef6 | 1917 | let mut nested_obligations = Vec::new(); |
3c0e092e XL |
1918 | let obligation_projection = obligation.predicate; |
1919 | let obligation_projection = ensure_sufficient_stack(|| { | |
1920 | normalize_with_depth_to( | |
1921 | selcx, | |
1922 | obligation.param_env, | |
1923 | obligation.cause.clone(), | |
1924 | obligation.recursion_depth + 1, | |
1925 | obligation_projection, | |
1926 | &mut nested_obligations, | |
1927 | ) | |
1928 | }); | |
6a06907d | 1929 | let cache_projection = if potentially_unnormalized_candidate { |
29967ef6 XL |
1930 | ensure_sufficient_stack(|| { |
1931 | normalize_with_depth_to( | |
1932 | selcx, | |
1933 | obligation.param_env, | |
1934 | obligation.cause.clone(), | |
1935 | obligation.recursion_depth + 1, | |
6a06907d | 1936 | cache_projection, |
29967ef6 XL |
1937 | &mut nested_obligations, |
1938 | ) | |
1939 | }) | |
1940 | } else { | |
6a06907d | 1941 | cache_projection |
29967ef6 XL |
1942 | }; |
1943 | ||
3c0e092e XL |
1944 | debug!(?cache_projection, ?obligation_projection); |
1945 | ||
6a06907d | 1946 | match infcx.at(cause, param_env).eq(cache_projection, obligation_projection) { |
29967ef6 XL |
1947 | Ok(InferOk { value: _, obligations }) => { |
1948 | nested_obligations.extend(obligations); | |
1949 | assoc_ty_own_obligations(selcx, obligation, &mut nested_obligations); | |
5099ac24 FG |
1950 | // FIXME(associated_const_equality): Handle consts here as well? Maybe this progress type should just take |
1951 | // a term instead. | |
1952 | Progress { term: cache_entry.term, obligations: nested_obligations } | |
29967ef6 | 1953 | } |
ba9703b0 XL |
1954 | Err(e) => { |
1955 | let msg = format!( | |
1956 | "Failed to unify obligation `{:?}` with poly_projection `{:?}`: {:?}", | |
1957 | obligation, poly_cache_entry, e, | |
1958 | ); | |
1959 | debug!("confirm_param_env_candidate: {}", msg); | |
f035d41b | 1960 | let err = infcx.tcx.ty_error_with_message(obligation.cause.span, &msg); |
5099ac24 | 1961 | Progress { term: err.into(), obligations: vec![] } |
ba9703b0 XL |
1962 | } |
1963 | } | |
1964 | } | |
1965 | ||
1966 | fn confirm_impl_candidate<'cx, 'tcx>( | |
1967 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
1968 | obligation: &ProjectionTyObligation<'tcx>, | |
f035d41b | 1969 | impl_impl_source: ImplSourceUserDefinedData<'tcx, PredicateObligation<'tcx>>, |
ba9703b0 XL |
1970 | ) -> Progress<'tcx> { |
1971 | let tcx = selcx.tcx(); | |
1972 | ||
29967ef6 | 1973 | let ImplSourceUserDefinedData { impl_def_id, substs, mut nested } = impl_impl_source; |
ba9703b0 XL |
1974 | let assoc_item_id = obligation.predicate.item_def_id; |
1975 | let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap(); | |
1976 | ||
1977 | let param_env = obligation.param_env; | |
ee023bcb FG |
1978 | let Ok(assoc_ty) = assoc_def(selcx, impl_def_id, assoc_item_id) else { |
1979 | return Progress { term: tcx.ty_error().into(), obligations: nested }; | |
ba9703b0 XL |
1980 | }; |
1981 | ||
1982 | if !assoc_ty.item.defaultness.has_value() { | |
1983 | // This means that the impl is missing a definition for the | |
1984 | // associated type. This error will be reported by the type | |
1985 | // checker method `check_impl_items_against_trait`, so here we | |
1986 | // just return Error. | |
1987 | debug!( | |
1988 | "confirm_impl_candidate: no associated type {:?} for {:?}", | |
5099ac24 | 1989 | assoc_ty.item.name, obligation.predicate |
ba9703b0 | 1990 | ); |
5099ac24 | 1991 | return Progress { term: tcx.ty_error().into(), obligations: nested }; |
ba9703b0 | 1992 | } |
f035d41b XL |
1993 | // If we're trying to normalize `<Vec<u32> as X>::A<S>` using |
1994 | //`impl<T> X for Vec<T> { type A<Y> = Box<Y>; }`, then: | |
1995 | // | |
1996 | // * `obligation.predicate.substs` is `[Vec<u32>, S]` | |
1997 | // * `substs` is `[u32]` | |
1998 | // * `substs` ends up as `[u32, S]` | |
ba9703b0 XL |
1999 | let substs = obligation.predicate.substs.rebase_onto(tcx, trait_def_id, substs); |
2000 | let substs = | |
2001 | translate_substs(selcx.infcx(), param_env, impl_def_id, substs, assoc_ty.defining_node); | |
f035d41b | 2002 | let ty = tcx.type_of(assoc_ty.item.def_id); |
5099ac24 FG |
2003 | let is_const = matches!(tcx.def_kind(assoc_ty.item.def_id), DefKind::AssocConst); |
2004 | let term: ty::Term<'tcx> = if is_const { | |
2005 | let identity_substs = | |
2006 | crate::traits::InternalSubsts::identity_for_item(tcx, assoc_ty.item.def_id); | |
2007 | let did = ty::WithOptConstParam::unknown(assoc_ty.item.def_id); | |
2008 | let val = ty::ConstKind::Unevaluated(ty::Unevaluated::new(did, identity_substs)); | |
2009 | tcx.mk_const(ty::ConstS { ty, val }).into() | |
2010 | } else { | |
2011 | ty.into() | |
2012 | }; | |
ba9703b0 | 2013 | if substs.len() != tcx.generics_of(assoc_ty.item.def_id).count() { |
f035d41b | 2014 | let err = tcx.ty_error_with_message( |
29967ef6 | 2015 | obligation.cause.span, |
f035d41b XL |
2016 | "impl item and trait item have different parameter counts", |
2017 | ); | |
5099ac24 | 2018 | Progress { term: err.into(), obligations: nested } |
ba9703b0 | 2019 | } else { |
29967ef6 | 2020 | assoc_ty_own_obligations(selcx, obligation, &mut nested); |
5099ac24 | 2021 | Progress { term: term.subst(tcx, substs), obligations: nested } |
ba9703b0 XL |
2022 | } |
2023 | } | |
2024 | ||
29967ef6 XL |
2025 | // Get obligations corresponding to the predicates from the where-clause of the |
2026 | // associated type itself. | |
2027 | // Note: `feature(generic_associated_types)` is required to write such | |
ee023bcb | 2028 | // predicates, even for non-generic associated types. |
29967ef6 XL |
2029 | fn assoc_ty_own_obligations<'cx, 'tcx>( |
2030 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
2031 | obligation: &ProjectionTyObligation<'tcx>, | |
2032 | nested: &mut Vec<PredicateObligation<'tcx>>, | |
2033 | ) { | |
2034 | let tcx = selcx.tcx(); | |
2035 | for predicate in tcx | |
2036 | .predicates_of(obligation.predicate.item_def_id) | |
2037 | .instantiate_own(tcx, obligation.predicate.substs) | |
2038 | .predicates | |
2039 | { | |
2040 | let normalized = normalize_with_depth_to( | |
2041 | selcx, | |
2042 | obligation.param_env, | |
2043 | obligation.cause.clone(), | |
2044 | obligation.recursion_depth + 1, | |
fc512014 | 2045 | predicate, |
29967ef6 XL |
2046 | nested, |
2047 | ); | |
2048 | nested.push(Obligation::with_depth( | |
2049 | obligation.cause.clone(), | |
2050 | obligation.recursion_depth + 1, | |
2051 | obligation.param_env, | |
2052 | normalized, | |
2053 | )); | |
2054 | } | |
2055 | } | |
2056 | ||
ba9703b0 XL |
2057 | /// Locate the definition of an associated type in the specialization hierarchy, |
2058 | /// starting from the given impl. | |
2059 | /// | |
2060 | /// Based on the "projection mode", this lookup may in fact only examine the | |
2061 | /// topmost impl. See the comments for `Reveal` for more details. | |
5099ac24 | 2062 | fn assoc_def( |
ba9703b0 XL |
2063 | selcx: &SelectionContext<'_, '_>, |
2064 | impl_def_id: DefId, | |
5099ac24 | 2065 | assoc_def_id: DefId, |
ee023bcb | 2066 | ) -> Result<specialization_graph::LeafDef, ErrorGuaranteed> { |
ba9703b0 | 2067 | let tcx = selcx.tcx(); |
ba9703b0 XL |
2068 | let trait_def_id = tcx.impl_trait_ref(impl_def_id).unwrap().def_id; |
2069 | let trait_def = tcx.trait_def(trait_def_id); | |
2070 | ||
2071 | // This function may be called while we are still building the | |
2072 | // specialization graph that is queried below (via TraitDef::ancestors()), | |
2073 | // so, in order to avoid unnecessary infinite recursion, we manually look | |
2074 | // for the associated item at the given impl. | |
2075 | // If there is no such item in that impl, this function will fail with a | |
2076 | // cycle error if the specialization graph is currently being built. | |
5099ac24 FG |
2077 | if let Some(&impl_item_id) = tcx.impl_item_implementor_ids(impl_def_id).get(&assoc_def_id) { |
2078 | let item = tcx.associated_item(impl_item_id); | |
2079 | let impl_node = specialization_graph::Node::Impl(impl_def_id); | |
2080 | return Ok(specialization_graph::LeafDef { | |
2081 | item: *item, | |
2082 | defining_node: impl_node, | |
2083 | finalizing_node: if item.defaultness.is_default() { None } else { Some(impl_node) }, | |
2084 | }); | |
ba9703b0 XL |
2085 | } |
2086 | ||
2087 | let ancestors = trait_def.ancestors(tcx, impl_def_id)?; | |
5099ac24 | 2088 | if let Some(assoc_item) = ancestors.leaf_def(tcx, assoc_def_id) { |
ba9703b0 XL |
2089 | Ok(assoc_item) |
2090 | } else { | |
2091 | // This is saying that neither the trait nor | |
2092 | // the impl contain a definition for this | |
2093 | // associated type. Normally this situation | |
2094 | // could only arise through a compiler bug -- | |
2095 | // if the user wrote a bad item name, it | |
2096 | // should have failed in astconv. | |
5099ac24 FG |
2097 | bug!( |
2098 | "No associated type `{}` for {}", | |
2099 | tcx.item_name(assoc_def_id), | |
2100 | tcx.def_path_str(impl_def_id) | |
2101 | ) | |
ba9703b0 XL |
2102 | } |
2103 | } | |
2104 | ||
a2a8927a | 2105 | crate trait ProjectionCacheKeyExt<'cx, 'tcx>: Sized { |
ba9703b0 XL |
2106 | fn from_poly_projection_predicate( |
2107 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
f9f354fc | 2108 | predicate: ty::PolyProjectionPredicate<'tcx>, |
ba9703b0 XL |
2109 | ) -> Option<Self>; |
2110 | } | |
2111 | ||
a2a8927a | 2112 | impl<'cx, 'tcx> ProjectionCacheKeyExt<'cx, 'tcx> for ProjectionCacheKey<'tcx> { |
ba9703b0 XL |
2113 | fn from_poly_projection_predicate( |
2114 | selcx: &mut SelectionContext<'cx, 'tcx>, | |
f9f354fc | 2115 | predicate: ty::PolyProjectionPredicate<'tcx>, |
ba9703b0 XL |
2116 | ) -> Option<Self> { |
2117 | let infcx = selcx.infcx(); | |
2118 | // We don't do cross-snapshot caching of obligations with escaping regions, | |
2119 | // so there's no cache key to use | |
2120 | predicate.no_bound_vars().map(|predicate| { | |
2121 | ProjectionCacheKey::new( | |
2122 | // We don't attempt to match up with a specific type-variable state | |
2123 | // from a specific call to `opt_normalize_projection_type` - if | |
2124 | // there's no precise match, the original cache entry is "stranded" | |
2125 | // anyway. | |
fc512014 | 2126 | infcx.resolve_vars_if_possible(predicate.projection_ty), |
ba9703b0 XL |
2127 | ) |
2128 | }) | |
2129 | } | |
2130 | } |